B. Asavapibhop

The CEBAF large acceptance spectrometer (CLAS) is used to study photo- and electro-induced nuclear and hadronic reactions by providing efficient detection of neutral and charged particles over a good fraction of the full solid angle. A collaboration of about 30 institutions has designed, assembled, and commissioned CLAS in Hall B at the Thomas Jefferson National Accelerator Facility. The CLAS detector is based on a novel six-coil toroidal magnet which provides a largely azimuthal field distribution. Trajectory reconstruction using drift chambers results in a momentum resolution of 0.5% at forward angles. Cherenkov counters, time-of-flight scintillators, and electromagnetic calorimeters provide good particle identification. Fast triggering and high data-acquisition rates allow operation at a luminosity of 1034nucleoncm−2s−1. These capabilities are being used in a broad experimental program to study the structure and interactions of mesons, nucleons, and nuclei using polarized and unpolarized electron and photon beams and targets. This paper is a comprehensive and general description of the design, construction and performance of CLAS.

In an exclusive measurement of the reaction gammad-->K(+)K(-)pn, a narrow peak that can be attributed to an exotic baryon with strangeness S=+1 is seen in the K(+)n invariant mass spectrum. The peak is at 1.542+/-0.005 GeV/c(2) with a measured width of 0.021 GeV/c(2) FWHM, which is largely determined by experimental mass resolution. The statistical significance of the peak is (5.2+/-0.6)sigma. The mass and width of the observed peak are consistent with recent reports of a narrow S=+1 baryon by other experimental groups.

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton LS detector at 700-m underground. An excellent energy resolution and a large fiducial volume offer exciting opportunities for addressing many important topics in neutrino and astro-particle physics. With 6 years of data, the neutrino mass ordering can be determined at 3-4 sigma and three oscillation parameters can be measured to a precision of 0.6% or better by detecting reactor antineutrinos. With 10 years of data, DSNB could be observed at 3-sigma; a lower limit of the proton lifetime of 8.34e33 years (90% C.L.) can be set by searching for p->nu_bar K^+; detection of solar neutrinos would shed new light on the solar metallicity problem and examine the vacuum-matter transition region. A core-collapse supernova at 10 kpc would lead to ~5000 IBD and ~2000 (300) all-flavor neutrino-proton (electron) scattering events. Geo-neutrinos can be detected with a rate of ~400 events/year. We also summarize the final design of the JUNO detector and the key R&D achievements. All 20-inch PMTs have been tested. The average photon detection efficiency is 28.9% for the 15,000 MCP PMTs and 28.1% for the 5,000 dynode PMTs, higher than the JUNO requirement of 27%. Together with the >20 m attenuation length of LS, we expect a yield of 1345 p.e. per MeV and an effective energy resolution of 3.02%/\sqrt{E (MeV)}$ in simulations. The underwater electronics is designed to have a loss rate <0.5% in 6 years. With degassing membranes and a micro-bubble system, the radon concentration in the 35-kton water pool could be lowered to <10 mBq/m^3. Acrylic panels of radiopurity <0.5 ppt U/Th are produced. The 20-kton LS will be purified onsite. Singles in the fiducial volume can be controlled to ~10 Hz. The JUNO experiment also features a double calorimeter system with 25,600 3-inch PMTs, a LS testing facility OSIRIS, and a near detector TAO.

High-statistics cross sections for the reactions gamma + p --> K^+ + Lambda and gamma + p --> K^+ + Sigma^0 have been measured using CLAS at Jefferson Lab for center-of-mass energies W between 1.6 and 2.53 GeV, and for -0.85 < cos theta_{K^+}^{c.m.}< +0.95. In the K^+ Lambda channel we confirm a resonance-like structure near W=1.9 GeV at backward kaon angles. The position and width of this structure change with angle, indicating that more than one resonance is likely playing a role. The K^+ Lambda channel at forward angles and all energies is well described by a t-channel scaling characteristic of Regge exchange, while the same scaling applied to the K^+ Sigma^0 channel is less successful. Several existing theoretical models are compared to the data, but none provide a good representation of the results.

We report the first results of the beam-spin asymmetry measured in the reaction $\stackrel{\ensuremath{\rightarrow}}{e}p\ensuremath{\rightarrow}\mathrm{ep}\ensuremath{\gamma}$ at a beam energy of 4.25 GeV. A large asymmetry with a $\mathrm{sin}\ensuremath{\varphi}$ modulation is observed, as predicted for the interference term of deeply virtual compton scattering (DVCS) and the Bethe-Heitler process. The amplitude of this modulation is $\ensuremath{\alpha}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.202\ifmmode\pm\else\textpm\fi{}0.028$. In leading-order and leading-twist perturbative QCD, the $\ensuremath{\alpha}$ is directly proportional to the imaginary part of the DVCS amplitude.

The reaction gamma p-->pi(+)K(-)K(+)n was studied at Jefferson Laboratory using a tagged photon beam with an energy range of 3-5.47 GeV. A narrow baryon state with strangeness S=+1 and mass M=1555+/-10 MeV/c(2) was observed in the nK(+) invariant mass spectrum. The peak's width is consistent with the CLAS resolution (FWHM=26 MeV/c(2)), and its statistical significance is (7.8+/-1.0)sigma. A baryon with positive strangeness has exotic structure and cannot be described in the framework of the naive constituent quark model. The mass of the observed state is consistent with the mass predicted by the chiral soliton model for the Theta(+) baryon. In addition, the pK(+) invariant mass distribution was analyzed in the reaction gamma p-->K(-)K(+)p with high statistics in search of doubly charged exotic baryon states. No resonance structures were found in this spectrum.

The ratios of inclusive electron scattering cross sections of 4 He, 12 C and 56 Fe to 3 He have been measured at 1 < xB < 3.At Q 2 > 1.4 GeV 2 , the ratios exhibit two separate plateaus, at 1.5 < xB < 2 and at xB > 2.25.This pattern is predicted by models that include 2-and 3-nucleon short-range correlations (SRC).Relative to A = 3, the per-nucleon probabilities of 3-nucleon SRC are 2.3, 3.2, and 4.6 times larger for A = 4, 12 and 56.This is the first measurement of 3-nucleon SRC probabilities in nuclei.

Models of baryon structure predict a small quadrupole deformation of the nucleon due to residual tensor forces between quarks or distortions from the pion cloud. Sensitivity to quark versus pion degrees of freedom occurs through the Q2 dependence of the magnetic (M1+), electric (E1+), and scalar (S1+) multipoles in the gamma*p-->Delta(+)-->p pi(0) transition. We report new experimental values for the ratios E(1+)/M(1+) and S(1+)/M(1+) over the range Q2 = 0.4-1.8 GeV2, extracted from precision p(e,e(')p)pi(0) data using a truncated multipole expansion. Results are best described by recent unitary models in which the pion cloud plays a dominant role.

Cross-sections and recoil polarizations for the reactions gamma + p --> K^+ + Lambda and gamma + p --> K^+ + Sigma^0 have been measured with high statistics and with good angular coverage for center-of-mass energies between 1.6 and 2.3 GeV. In the K^+Lambda channel we confirm a structure near W=1.9 GeV at backward kaon angles, but our data shows a more complex s- and u- channel resonance structure than previously seen. This structure is present at forward and backward angles but not central angles, and its position and width change with angle, indicating that more than one resonance is playing a role. Rising back-angle cross sections at higher energies and large positive polarization at backward angles are consistent with sizable s- or u-channel contributions. None of the model calculations we present can consistently explain these aspects of the data.

Spin transfer from circularly polarized real photons to recoiling hyperons has been measured for the reactions $\vec\gamma + p \to K^+ + \vec\Lambda$ and $\vec\gamma + p \to K^+ + \vec\Sigma^0$. The data were obtained using the CLAS detector at Jefferson Lab for center-of-mass energies $W$ between 1.6 and 2.53 GeV, and for $-0.85<\cos\theta_{K^+}^{c.m.}< +0.95$. For the $\Lambda$, the polarization transfer coefficient along the photon momentum axis, $C_z$, was found to be near unity for a wide range of energy and kaon production angles. The associated transverse polarization coefficient, $C_x$, is smaller than $C_z$ by a roughly constant difference of unity. Most significantly, the {\it total} $\Lambda$ polarization vector, including the induced polarization $P$, has magnitude consistent with unity at all measured energies and production angles when the beam is fully polarized. For the $\Sigma^0$ this simple phenomenology does not hold. All existing hadrodynamic models are in poor agreement with these results.

A bstract We present the calibration strategy for the 20 kton liquid scintillator central detector of the Jiangmen Underground Neutrino Observatory (JUNO). By utilizing a comprehensive multiple-source and multiple-positional calibration program, in combination with a novel dual calorimetry technique exploiting two independent photosensors and readout systems, we demonstrate that the JUNO central detector can achieve a better than 1% energy linearity and a 3% effective energy resolution, required by the neutrino mass ordering determination.

The core-collapse supernova (CCSN) is considered one of the most energetic astrophysical events in the universe. The early and prompt detection of neutrinos before (pre-SN) and during the supernova (SN) burst presents a unique opportunity for multi-messenger observations of CCSN events. In this study, we describe the monitoring concept and present the sensitivity of the system to pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton liquid scintillator detector currently under construction in South China. The real-time monitoring system is designed to ensure both prompt alert speed and comprehensive coverage of progenitor stars. It incorporates prompt monitors on the electronic board as well as online monitors at the data acquisition stage. Assuming a false alert rate of 1 per year, this monitoring system exhibits sensitivity to pre-SN neutrinos up to a distance of approximately 1.6 (0.9) kiloparsecs and SN neutrinos up to about 370 (360) kiloparsecs for a progenitor mass of 30 solar masses, considering both normal and inverted mass ordering scenarios. The pointing ability of the CCSN is evaluated by analyzing the accumulated event anisotropy of inverse beta decay interactions from pre-SN or SN neutrinos. This, along with the early alert, can play a crucial role in facilitating follow-up multi-messenger observations of the next galactic or nearby extragalactic CCSN.

The ratios of inclusive electron scattering cross sections of $^4$He, $^{12}$C, and $^{56}$Fe to $^3$He have been measured for the first time. It is shown that these ratios are independent of $x_B$ at Q$^2>$1.4 (GeV/c)$^2$ for $x_B>$ 1.5 where the inclusive cross section depends primarily on the high-momentum components of the nuclear wave function. The observed scaling shows that the momentum distributions at high-momenta have the same shape for all nuclei and differ only by a scale factor. The observed onset of the scaling at Q$^2>$1.4 and $x_B >$1.5 is consistent with the kinematical expectation that two nucleon short range correlations (SRC) are dominate the nuclear wave function at $p_m\gtrsim$ 300 MeV/c. The values of these ratios in the scaling region can be related to the relative probabilities of SRC in nuclei with A$\ge$3. Our data demonstrate that for nuclei with A$\geq$12 these probabilities are 5-5.5 times larger than in deuterium, while for $^4$He it is larger by a factor of about 3.5.

We report the first evidence for a nonzero beam-spin azimuthal asymmetry in the electroproduction of positive pions in the deep-inelastic kinematic region. Data for the reaction $e\stackrel{\ensuremath{\rightarrow}}{p}{e}^{\ensuremath{'}}{\ensuremath{\pi}}^{+}X$ have been obtained using a polarized electron beam of 4.3 GeV with the CEBAF Large Acceptance Spectrometer at the Thomas Jefferson National Accelerator Facility. The amplitude of the $\mathrm{sin}\ensuremath{\varphi}$ modulation increases with the momentum of the pion relative to the virtual photon, z. In the range $z=0.5--0.8$ the average amplitude is $0.038\ifmmode\pm\else\textpm\fi{}0.005\ifmmode\pm\else\textpm\fi{}0.003$ for a missing mass ${M}_{X}&gt;1.1\mathrm{GeV}$ and $0.037\ifmmode\pm\else\textpm\fi{}0.007\ifmmode\pm\else\textpm\fi{}0.004$ for ${M}_{X}&gt;1.4\mathrm{GeV}.$

The neutron elastic magnetic form factor GMn has been extracted from quasielastic electron scattering data on deuterium with the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic coverage of the measurement is continuous from Q2=1 GeV2 to 4.8 GeV2. High precision was achieved by employing a ratio technique in which many uncertainties cancel, and by a simultaneous in-situ calibration of the neutron detection efficiency, the largest correction to the data. Neutrons were detected using the CLAS electromagnetic calorimeters and the time-of-flight scintillators. Data were taken at two different electron beam energies, allowing up to four semi-independent measurements of GMn to be made at each value of Q2. The dipole parameterization is found to provide a good description of the data over the measured Q2 range.

To maximize the light yield of the liquid scintillator (LS) for the Jiangmen Underground Neutrino Observatory (JUNO), a 20 t LS sample was produced in a pilot plant at Daya Bay. The optical properties of the new LS in various compositions were studied by replacing the gadolinium-loaded LS in one antineutrino detector. The concentrations of the fluor, PPO, and the wavelength shifter, bis-MSB, were increased in 12 steps from 0.5 g/L and <0.01 mg/L to 4 g/L and 13 mg/L, respectively. The numbers of total detected photoelectrons suggest that, with the optically purified solvent, the bis-MSB concentration does not need to be more than 4 mg/L. To bridge the one order of magnitude in the detector size difference between Daya Bay and JUNO, the Daya Bay data were used to tune the parameters of a newly developed optical model. Then, the model and tuned parameters were used in the JUNO simulation. This enabled to determine the optimal composition for the JUNO LS: purified solvent LAB with 2.5 g/L PPO, and 1 to 4 mg/L bis-MSB.

Abstract The Jiangmen Underground Neutrino Observatory (JUNO) features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent location for <?CDATA $ ^8 $?> B solar neutrino measurements, such as its low-energy threshold, high energy resolution compared with water Cherenkov detectors, and much larger target mass compared with previous liquid scintillator detectors. In this paper, we present a comprehensive assessment of JUNO's potential for detecting <?CDATA $ ^8 $?> B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2 MeV threshold for the recoil electron energy is found to be achievable, assuming that the intrinsic radioactive background <?CDATA $ ^{238} $?> U and <?CDATA $ ^{232} $?> Th in the liquid scintillator can be controlled to 10 <?CDATA $ ^{-17} $?> g/g. With ten years of data acquisition, approximately 60,000 signal and 30,000 background events are expected. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter, which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework. If <?CDATA $ \Delta m^{2}_{21} = 4.8\times10^{-5}\; (7.5\times10^{-5}) $?> eV <?CDATA $ ^{2} $?> , JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3 <?CDATA $ \sigma $?> (2 <?CDATA $ \sigma $?> ) level by measuring the non-zero signal rate variation with respect to the solar zenith angle. Moreover, JUNO can simultaneously measure <?CDATA $ \Delta m^2_{21} $?> using <?CDATA $ ^8 $?> B solar neutrinos to a precision of 20% or better, depending on the central value, and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of <?CDATA $ \Delta m^2_{21} $?> reported by solar neutrino experiments and the KamLAND experiment.

Abstract Main goal of the JUNO experiment is to determine the neutrino mass ordering using a 20 kt liquid-scintillator detector. Its key feature is an excellent energy resolution of at least 3% at 1 MeV, for which its instruments need to meet a certain quality and thus have to be fully characterized. More than 20,000 20-inch PMTs have been received and assessed by JUNO after a detailed testing program which began in 2017 and elapsed for about four years. Based on this mass characterization and a set of specific requirements, a good quality of all accepted PMTs could be ascertained. This paper presents the performed testing procedure with the designed testing systems as well as the statistical characteristics of all 20-inch PMTs intended to be used in the JUNO experiment, covering more than fifteen performance parameters including the photocathode uniformity. This constitutes the largest sample of 20-inch PMTs ever produced and studied in detail to date, i.e. 15,000 of the newly developed 20-inch MCP-PMTs from Northern Night Vision Technology Co. (NNVT) and 5000 of dynode PMTs from Hamamatsu Photonics K. K.(HPK).

Differential cross sections for gammap-->etap have been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV. Mesons were identified by missing mass reconstruction using kinematical information for protons scattered in the production process. The data provide the first extensive angular distribution measurements for the process above W=1.75 GeV. Comparison with preliminary results from a constituent quark model support the suggestion that a third S11 resonance with mass approximately 1.8 GeV couples to the etaN channel.

New cross sections for the reaction e p-->e p eta are reported for total center of mass energy W = 1.5--1.86 GeV and invariant momentum transfer Q2 = 0.25--1.5 (GeV/c)(2). This large kinematic range allows extraction of important new information about response functions, photocouplings, and eta N coupling strengths of baryon resonances. Newly observed structure at W approximately 1.65 GeV is shown to come from interference between S and P waves and can be interpreted with known resonances. Improved values are derived for the photon coupling amplitude for the S11(1535) resonance.

The cross section for the reaction ep-->e(')ppi(+)pi(-) was measured in the resonance region for 1.4<W<2.1 GeV and 0.5<Q2<1.5 GeV(2)/c(2) using the CLAS detector at Jefferson Laboratory. The data show resonant structures not visible in previous experiments. The comparison of our data to a phenomenological prediction using available information on N(*) and Delta states shows an evident discrepancy. A better description of the data is obtained either by a sizable change of the properties of the P13(1720) resonance or by introducing a new baryon state, not reported in published analyses.

Experimental Hall B at Jefferson Laboratory houses the CEBAF Large Acceptance Spectrometer, the magnetic field of which is produced by a superconducting toroid. The six coils of this toroid divide the detector azimuthally into six sectors, each of which contains three large multi-layer drift chambers for tracking charged particles produced from a fixed target on the toroidal axis. Within the 18 drift chambers are a total of 35,148 individually instrumented hexagonal drift cells. The novel geometry of these chambers provides for good tracking resolution and efficiency, along with large acceptance. The design and construction challenges posed by these large-scale detectors are described, and detailed results are presented from in-beam measurements.

Differential cross sections for the reaction $\gamma p \to p \pi^0$ have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged photon beam with energies from 0.675 to 2.875 GeV. The results reported here possess greater accuracy in the absolute normalization than previous measurements. They disagree with recent CB-ELSA measurements for the process at forward scattering angles. Agreement with the SAID and MAID fits is found below 1 GeV. The present set of cross sections has been incorporated into the SAID database, and exploratory fits have been extended to 3 GeV. Resonance couplings have been extracted and compared to previous determinations.

Abstract We present the detection potential for the diffuse supernova neutrino background (DSNB) at the Jiangmen Underground Neutrino Observatory (JUNO), using the inverse-beta-decay (IBD) detection channel on free protons. We employ the latest information on the DSNB flux predictions, and investigate in detail the background and its reduction for the DSNB search at JUNO. The atmospheric neutrino induced neutral current (NC) background turns out to be the most critical background, whose uncertainty is carefully evaluated from both the spread of model predictions and an envisaged in situ measurement. We also make a careful study on the background suppression with the pulse shape discrimination (PSD) and triple coincidence (TC) cuts. With latest DSNB signal predictions, more realistic background evaluation and PSD efficiency optimization, and additional TC cut, JUNO can reach the significance of 3σ for 3 years of data taking, and achieve better than 5σ after 10 years for a reference DSNB model. In the pessimistic scenario of non-observation, JUNO would strongly improve the limits and exclude a significant region of the model parameter space.

Double-polarization asymmetries for inclusive ep scattering were measured at Jefferson Lab using 2.6 and 4.3 GeV longitudinally polarized electrons incident on a longitudinally polarized NH3 target in the CLAS detector. The polarized structure function g(1)(x,Q2) was extracted throughout the nucleon resonance region and into the deep inelastic regime, for Q(2)=0.15-1.64 GeV2. The contributions to the first moment Gamma(1)(Q2)= integral g(1)(x,Q2) dx were determined up to Q(2)=1.2 GeV2. Using a parametrization for g(1) in the unmeasured low x regions, the complete first moment was estimated over this Q2 region. A rapid change in Gamma(1) is observed for Q2<1 GeV2, with a sign change near Q(2)=0.3 GeV2, indicating dominant contributions from the resonance region. At Q(2)=1.2 GeV2 our data are below the perturbative QCD evolved scaling value.

Received 21 January 2004DOI:https://doi.org/10.1103/PhysRevLett.92.049902©2004 American Physical Society

The $\mathit{ep}\ensuremath{\rightarrow}{e}^{'}{\ensuremath{\pi}}^{+}n$ reaction was studied in the first and second nucleon resonance regions in the $0.25$ GeV${}^{2}&lt;{Q}^{2}&lt;0.65$ GeV${}^{2}$ range by use of the CLAS detector at Thomas Jefferson National Accelerator Facility. For the first time, to our knowledge, the absolute cross sections were measured, covering nearly the full angular range in the hadronic center-of-mass frame. We extracted the structure functions ${\ensuremath{\sigma}}_{\mathit{TL}},{\ensuremath{\sigma}}_{\mathit{TT}}$, and the linear combination ${\ensuremath{\sigma}}_{T}+\ensuremath{\epsilon}{\ensuremath{\sigma}}_{L}$ by fitting the $\ensuremath{\phi}$ dependence of the measured cross sections and compared them with the MAID and Sato-Lee models.

We report measurements of the exclusive electroproduction of ${K}^{+}\ensuremath{\Lambda}$ and ${K}^{+}{\ensuremath{\Sigma}}^{0}$ final states from a proton target using the Continuous Electron Beam Accelerator Facility (CEBAF) large-acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility. The separated structure functions ${\ensuremath{\sigma}}_{T},{\ensuremath{\sigma}}_{L},{\ensuremath{\sigma}}_{\mathit{TT}}$, and ${\ensuremath{\sigma}}_{\mathit{LT}}$ were extracted from the \ensuremath{\Phi}- and \ensuremath{\epsilon}-dependent differential cross sections taken with electron beam energies of 2.567, 4.056, and 4.247 GeV. This analysis represents the first ${\ensuremath{\sigma}}_{L}/{\ensuremath{\sigma}}_{T}$ separation with the CLAS detector, and the first measurement of the kaon electroproduction structure functions away from parallel kinematics. The data span a broad range of momentum transfers from $0.5\ensuremath{\leqslant}{Q}^{2}\ensuremath{\leqslant}2.8{\mathrm{GeV}}^{2}$ and invariant energy from $1.6\ensuremath{\leqslant}W\ensuremath{\leqslant}2.4$ GeV, while spanning nearly the full center-of-mass angular range of the kaon. The separated structure functions reveal clear differences between the production dynamics for the \ensuremath{\Lambda} and ${\ensuremath{\Sigma}}^{0}$ hyperons. These results provide an unprecedented data sample with which to constrain current and future models for the associated production of strangeness, which will allow for a better understanding of the underlying resonant and nonresonant contributions to hyperon production.

ABSTRACT Neutron monitors (NMs) are ground-based detectors of cosmic-ray showers that are widely used for high-precision monitoring of changes in the Galactic cosmic-ray (GCR) flux due to solar storms and solar wind variations. In the present work, we show that a single neutron monitor station can also monitor short-term changes in the GCR spectrum, avoiding the systematic uncertainties in comparing data from different stations, by means of NM time-delay histograms. Using data for 2007–2014 from the Princess Sirindhorn Neutron Monitor , a station at Doi Inthanon, Thailand, with the world’s highest vertical geomagnetic cutoff rigidity of 16.8 GV, we have developed an analysis of time-delay histograms that removes the chance coincidences that can dominate conventional measures of multiplicity. We infer the “leader fraction” L of neutron counts that do not follow a previous neutron count in the same counter from the same atmospheric secondary, which is inversely related to the actual multiplicity and increases for increasing GCR spectral index. After correction for atmospheric pressure and water vapor, we find that L indicates substantial short-term GCR spectral hardening during some but not all Forbush decreases in GCR flux due to solar storms. Such spectral data from Doi Inthanon provide information about cosmic-ray energies beyond the Earth’s maximum geomagnetic cutoff, extending the reach of the worldwide NM network and opening a new avenue in the study of short-term GCR decreases.

We measured the inclusive electron-proton cross section in the nucleon resonance region $(W&lt;2.5\mathrm{GeV})$ at momentum transfers ${Q}^{2}$ below $4.5(\mathrm{GeV}{/c)}^{2}$ with the CLAS detector. The large acceptance of CLAS allowed the measurement of the cross section in a large, contiguous two-dimensional range of ${Q}^{2}$ and x, making it possible to perform an integration of the data at fixed ${Q}^{2}$ over the significant x interval. From these data we extracted the structure function ${F}_{2}$ and, by including other world data, we studied the ${Q}^{2}$ evolution of its moments, ${M}_{n}{(Q}^{2}),$ in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and will require significant improvements in theoretical predictions if a meaningful comparison with these new experimental results is to be made.

The first measurements of the transferred polarization for the exclusive e-->p-->e(')K+Lambda--> reaction have been performed at Jefferson Laboratory using the CLAS spectrometer. A 2.567 GeV beam was used to measure the hyperon polarization over Q2 from 0.3 to 1.5 (GeV/c)(2), W from 1.6 to 2.15 GeV, and over the full K+ center-of-mass angular range. Comparison with predictions of hadrodynamic models indicates strong sensitivity to the underlying resonance contributions. A nonrelativistic quark-model interpretation of our data suggests that the ssmacr; quark pair is produced with spins predominantly antialigned. Implications for the validity of the most widely used quark-pair creation operator are discussed.

The polarized longitudinal-transverse structure function $σ_{LT^\prime}$ has been measured in the $Δ(1232)$ resonance region at $Q^2=0.40$ and 0.65 GeV$^2$. Data for the $p(\vec e,e'p)π^o$ reaction were taken at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at an energy of 1.515 GeV. For the first time a complete angular distribution was measured, permitting the separation of different non-resonant amplitudes using a partial wave analysis. Comparison with previous beam asymmetry measurements at MAMI indicate a deviation from the predicted $Q^2$ dependence of $σ_{LT^{\prime}}$ using recent phenomenological models.

Differential cross sections for the reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}p$ have been measured with the CLAS spectrometer and a tagged photon beam with energies from 1.527 to 2.227 GeV. The results reported here possess much greater accuracy than previous measurements. Analyses of these data suggest for the first time the coupling of the ${\ensuremath{\eta}}^{\ensuremath{'}}N$ channel to both the ${S}_{11}(1535)$ and ${P}_{11}(1710)$ resonances, known to couple strongly to the $\ensuremath{\eta}N$ channel in photoproduction on the proton, and the importance of $J=3/2$ resonances in the process.

Abstract The OSIRIS detector is a subsystem of the liquid scintillator filling chain of the JUNO reactor neutrino experiment. Its purpose is to validate the radiopurity of the scintillator to assure that all components of the JUNO scintillator system work to specifications and only neutrino-grade scintillator is filled into the JUNO Central Detector. The aspired sensitivity level of $$10^{-16}\hbox { g/g}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>16</mml:mn> </mml:mrow> </mml:msup> <mml:mspace /> <mml:mtext>g/g</mml:mtext> </mml:mrow> </mml:math> of $$^{238}\hbox {U}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mrow /> <mml:mn>238</mml:mn> </mml:msup> <mml:mtext>U</mml:mtext> </mml:mrow> </mml:math> and $$^{232}\hbox {Th}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mrow /> <mml:mn>232</mml:mn> </mml:msup> <mml:mtext>Th</mml:mtext> </mml:mrow> </mml:math> requires a large ( $$\sim 20\,\hbox {m}^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>20</mml:mn> <mml:mspace /> <mml:msup> <mml:mtext>m</mml:mtext> <mml:mn>3</mml:mn> </mml:msup> </mml:mrow> </mml:math> ) detection volume and ultralow background levels. The present paper reports on the design and major components of the OSIRIS detector, the detector simulation as well as the measuring strategies foreseen and the sensitivity levels to U/Th that can be reached in this setup.

Beam-helicity asymmetries for the two-pion-photoproduction reaction gammap-->ppi(+)pi(-) have been studied for the first time in the resonance region for center-of-mass energies between 1.35 and 2.30 GeV. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer using circularly polarized tagged photons incident on an unpolarized hydrogen target. Beam-helicity-dependent angular distributions of the final-state particles were measured. The large cross-section asymmetries exhibit strong sensitivity to the kinematics and dynamics of the reaction. The data are compared with the results of various phenomenological model calculations, and show that these models currently do not provide an adequate description for the behavior of this new observable.

We investigate the transition from the nucleon-meson to quark-gluon description of the strong interaction using the photon energy dependence of the d(γ, p)n differential cross section for photon energies above 0.5 GeV and center-of-mass proton angles between 30 • and 150 • .A possible signature for this transition is the onset of cross section s -11 scaling with the total energy squared, s, at some proton transverse momentum, PT .The results show that the scaling has been reached for proton transverse momentum above about 1.1 GeV/c.This may indicate that the quark-gluon regime is reached above this momentum.

We report measurements of the beam spin asymmetry in Deeply Virtual Compton Scattering (DVCS) at an electron beam energy of 4.8 GeV using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The DVCS beam spin asymmetry has been measured in a wide range of kinematics, 1(GeV/c)$^2$ $<Q^2<2.8$(GeV/c)$^2$, $0.12<x_B<0.48$, and 0.1 (GeV/c)$^2$ $<-t<0.8$(GeV/c)$^2$, using the reaction \pEpX. The number of H$(e,e^{\prime}\gamma p)$ and H$(e,e^{\prime}\pi^0 p)$ events are separated in each $(Q^2,x_B,t)$ bin by a fit to the line shape of the H$(e,e^{\prime}p)X$ $M_x^2$ distribution. The validity of the method was studied in detail using experimental and simulated data. It was shown, that with the achieved missing mass squared resolution and the available statistics, the separation of DVCS-BH and $\pi^0$ events can reliably be done with less than 5% uncertainty. The $Q^2$- and $t$-dependences of the $\sin\phi$ moments of the asymmetry are extracted and compared with theoretical calculations.

A bstract JUNO is a massive liquid scintillator detector with a primary scientific goal of determining the neutrino mass ordering by studying the oscillated anti-neutrino flux coming from two nuclear power plants at 53 km distance. The expected signal anti-neutrino interaction rate is only 60 counts per day (cpd), therefore a careful control of the background sources due to radioactivity is critical. In particular, natural radioactivity present in all materials and in the environment represents a serious issue that could impair the sensitivity of the experiment if appropriate countermeasures were not foreseen. In this paper we discuss the background reduction strategies undertaken by the JUNO collaboration to reduce at minimum the impact of natural radioactivity. We describe our efforts for an optimized experimental design, a careful material screening and accurate detector production handling, and a constant control of the expected results through a meticulous Monte Carlo simulation program. We show that all these actions should allow us to keep the background count rate safely below the target value of 10 Hz (i.e. ∼ 1 cpd accidental background) in the default fiducial volume, above an energy threshold of 0.7 MeV.

Abstract The 3D range-modulator is a device used in particle delivery systems that can create a highly conformal and homogeneous dose distribution in the target volume with mono-energetic beams, providing an option for high dose-rate FLASH therapy. In the normal case, the modulators are positioned at a typical distance of 30-50 cm in front of the target in order to avoid the fluence ripples resulting from the periodic structure of the modulators. FLUKA Monte Carlo simulation package was used to investigate the fluence distributions of protons penetrating through the 2D range-modulator, the simplified version of the 3D range-modulator, and to determine the minimum distance at which the fluence is homogeneous enough for the treatment. To implement the complex geometry of the modulator in FLUKA, a dedicated FLUKA user routine was developed for the simulation of the periodic pin structures. The highest fluence ripple occurred at a few centimetres behind the modulators and then faded away as the distance increased, which can be described by the edge-scattering effect and later by the blur-out of the overlapping contributions from the pins. Moreover, the dose distribution in water was investigated, particularly for small distances between the modulators and the water phantom. Furthermore, the Monte Carlo results were compared with radiochromic film measurements irradiated with a 3D-printed range modulator and showed a good qualitative agreement. Prospectively, for low modulator-to-target distances, the strong dose inhomogeneities which appear in the proximal part of the target, could introduce additionally a kind of ‘mini beam’ normal-tissue sparing by the 3D range-modulators.

Abstract The Jiangmen Underground Neutrino Observatory (JUNO), the first multi-kton liquid scintillator detector, which is under construction in China, will have a unique potential to perform a real-time measurement of solar neutrinos well below the few MeV threshold typical of Water Cherenkov detectors. JUNO's large target mass and excellent energy resolution are prerequisites for reaching unprecedented levels of precision. In this paper, we provide estimation of the JUNO sensitivity to 7 Be, pep , and CNO solar neutrinos that can be obtained via a spectral analysis above the 0.45 MeV threshold. This study is performed assuming different scenarios of the liquid scintillator radiopurity, ranging from the most optimistic one corresponding to the radiopurity levels obtained by the Borexino experiment, up to the minimum requirements needed to perform the neutrino mass ordering determination with reactor antineutrinos — the main goal of JUNO. Our study shows that in most scenarios, JUNO will be able to improve the current best measurements on 7 Be, pep , and CNO solar neutrino fluxes. We also perform a study on the JUNO capability to detect periodical time variations in the solar neutrino flux, such as the day-night modulation induced by neutrino flavor regeneration in Earth, and the modulations induced by temperature changes driven by helioseismic waves.

The differential cross section, d sigma/dt, for rho(0) meson photoproduction on the proton above the resonance region was measured up to a momentum transfer -t = 5 GeV2 using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The rho(0) channel was extracted from the measured two charged-pion cross sections by fitting the pi(+)pi(-) and p pi(+) invariant masses. The low momentum transfer region shows the typical diffractive pattern expected from Reggeon exchange. The flatter behavior at large -t cannot be explained solely in terms of QCD-inspired two-gluon exchange models. The data indicate that other processes, like quark interchange, are important to fully describe rho photoproduction.

The differential cross section, dsigma/dt, for omega meson exclusive photoproduction on the proton above the resonance region (2.6<W<2.9 GeV) was measured up to a momentum transfer -t=5 GeV2 using the CLAS detector at Jefferson Laboratory. The omega channel was identified by detecting a proton and pi(+) in the final state and using the missing mass technique. While the low momentum transfer region shows the typical diffractive pattern expected from Pomeron and Reggeon exchange, at large -t the differential cross section has a flat behavior. This feature can be explained by introducing quark interchange processes in addition to the QCD-inspired two-gluon exchange.

Nearly complete angular distributions of the two-body deuteron photodisintegration differential cross section have been measured using the CEBAF Large Acceptance Spectrometer detector and the tagged photon beam at the Thomas Jefferson National Accelerator Facility. The data cover photon energies between $0.5$ and $3.0\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$ and center-of-mass proton scattering angles $10\ifmmode^\circ\else\textdegree\fi{}--160\ifmmode^\circ\else\textdegree\fi{}$. The data show a persistent forward-backward angle asymmetry over the explored energy range, and are well described by the nonperturbative quark gluon string model.

The first measurements of the polarized structure function ${\ensuremath{\sigma}}_{{\mathit{LT}}^{'}}$ for the reaction $^{1}\mathrm{H}$$(\stackrel{\ensuremath{\rightarrow}}{e},{e}^{'}{K}^{+})\ensuremath{\Lambda}$ in the nucleon resonance region are reported. Measurements are included from threshold up to $W=2.05$ GeV for central values of ${Q}^{2}$ of 0.65 and 1.00 GeV${}^{2}$, and nearly the entire kaon center-of-mass angular range. ${\ensuremath{\sigma}}_{{\mathit{LT}}^{'}}$ is the imaginary part of the longitudinal-transverse response and is expected to be sensitive to interferences between competing intermediate $s$-channel resonances, as well as resonant and nonresonant processes. The results for ${\ensuremath{\sigma}}_{{\mathit{LT}}^{'}}$ are comparable in magnitude to previously reported results from CLAS for ${\ensuremath{\sigma}}_{\mathit{LT}}$, the real part of the same response. An intriguing sign change in ${\ensuremath{\sigma}}_{{\mathit{LT}}^{'}}$ is observed in the high ${Q}^{2}$ data at $W\ensuremath{\approx}1.9$ GeV. Comparisons to several existing model predictions are shown.

This paper reports on the most comprehensive data set obtained on differential and fully integrated cross sections for the process $e p \to e' p \pi^{+} \pi^{-} $. The data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the so-far unexplored kinematic region of photon virtuality 0.2 $<$ $Q^{2}$ $<$ 0.6 GeV$^{2}$ and invariant mass of the final hadron system $W$ from 1.3 to 1.57 GeV. For the first time, nine independent 1-fold differential cross sections were determined in each bin of $W$ and $Q^{2}$ covered by the measurements. A phenomenological analysis of the data allowed us to establish the most significant mechanisms contributing to the reaction. The non-resonant mechanisms account for a major part of cross-sections. However, we find sensitivity to s-channel excitations of low-mass nucleon resonances, especially to the $N(1440)P_{11}$ and $N(1520)D_{13}$ states in kinematical dependencies of the 1-fold differential cross-sections.

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022.

We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer $[{Q}^{2}=0.27--1.3(\mathrm{GeV}{/c)}^{2}]$ and final hadronic state mass in the nucleon resonance region $(W=1.08--2.0\mathrm{GeV}).$ We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target ${(}^{15}{\mathrm{ND}}_{3})$ and detected the scattered electrons with the CEBAF large acceptance spectrometer. From our data, we extract the longitudinal double spin asymmetry ${A}_{||}$ and the spin structure function ${g}_{1}^{d}.$ Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function ${g}_{1}^{d}$ and study its approach to both the deep inelastic limit at large ${Q}^{2}$ and to the Gerasimov-Drell-Hearn sum rule at the real photon limit ${(Q}^{2}\ensuremath{\rightarrow}0).$ We find that the first moment varies rapidly in the ${Q}^{2}$ range of our experiment and crosses zero at ${Q}^{2}$ between 0.5 and $0.8(\mathrm{GeV}{/c)}^{2},$ indicating the importance of the $\ensuremath{\Delta}$ resonance at these momentum transfers.

We have measured the 3He(e,e'pp)n reaction at 2.2 GeV over a wide kinematic range. The kinetic energy distribution for `fast' nucleons (p > 250 MeV/c) peaks where two nucleons each have 20% or less, and the third nucleon has most of the transferred energy. These fast pp and pn pairs are back-to-back with little momentum along the three-momentum transfer, indicating that they are spectators. Experimental and theoretical evidence indicates that we have measured distorted two-nucleon momentum distributions by striking the third nucleon and detecting the spectator correlated pair.

The electromagnetic decays of the Σ0(1385) and Λ(1520) hyperons were studied in photon-induced reactions γp→K+Λ(1116)γ in the Large Acceptance Spectrometer detector at the Thomas Jefferson National Accelerator Facility. We report the first observation of the radiative decay of the Σ0(1385) and a measurement of the Λ(1520) radiative decay width. For the Σ0(1385)→Λ(1116)γ transition, we measured a partial width of 479±120(stat)+81−100(sys)keV, larger than all of the existing model predictions. For the Λ(1520)→Λ(1116)γ transition, we obtained a partial width of 167±43(stat)+26−12(sys)keV.12 MoreReceived 16 July 2004DOI:https://doi.org/10.1103/PhysRevC.71.054609©2005 American Physical Society

Atmospheric neutrinos are one of the most relevant natural neutrino sources that can be exploited to infer properties about cosmic rays and neutrino oscillations. The Jiangmen Underground Neutrino Observatory (JUNO) experiment, a 20 kton liquid scintillator detector with excellent energy resolution is currently under construction in China. JUNO will be able to detect several atmospheric neutrinos per day given the large volume. A study on the JUNO detection and reconstruction capabilities of atmospheric $\nu_e$ and $\nu_\mu$ fluxes is presented in this paper. In this study, a sample of atmospheric neutrino Monte Carlo events has been generated, starting from theoretical models, and then processed by the detector simulation. The excellent timing resolution of the 3'' PMT light detection system of JUNO detector and the much higher light yield for scintillation over Cherenkov allow to measure the time structure of the scintillation light with very high precision. Since $\nu_e$ and $\nu_\mu$ interactions produce a slightly different light pattern, the different time evolution of light allows to discriminate the flavor of primary neutrinos. A probabilistic unfolding method has been used, in order to infer the primary neutrino energy spectrum from the detector experimental observables. The simulated spectrum has been reconstructed between 100 MeV and 10 GeV, showing a great potential of the detector in the atmospheric low energy region.

The main task of the Top Tracker detector of the neutrino reactor experiment Jiangmen Underground Neutrino Observatory (JUNO) is to reconstruct and extrapolate atmospheric muon tracks down to the central detector. This muon tracker will help to evaluate the contribution of the cosmogenic background to the signal. The Top Tracker is located above JUNO's water Cherenkov Detector and Central Detector, covering about 60% of the surface above them. The JUNO Top Tracker is constituted by the decommissioned OPERA experiment Target Tracker modules. The technology used consists in walls of two planes of plastic scintillator strips, one per transverse direction. Wavelength shifting fibres collect the light signal emitted by the scintillator strips and guide it to both ends where it is read by multianode photomultiplier tubes. Compared to the OPERA Target Tracker, the JUNO Top Tracker uses new electronics able to cope with the high rate produced by the high rock radioactivity compared to the one in Gran Sasso underground laboratory. This paper will present the new electronics and mechanical structure developed for the Top Tracker of JUNO along with its expected performance based on the current detector simulation.

The main task of the Top Tracker detector of the neutrino reactor experiment Jiangmen Underground Neutrino Observatory (JUNO) is to reconstruct and extrapolate atmospheric muon tracks down to the central detector. This muon tracker will help to evaluate the contribution of the cosmogenic background to the signal. The Top Tracker is located above JUNO’s water Cherenkov Detector and Central Detector, covering about 60% of the surface above them. The JUNO Top Tracker is constituted by the decommissioned OPERA experiment Target Tracker modules. The technology used consists in walls of two planes of plastic scintillator strips, one per transverse direction. Wavelength shifting fibres collect the light signal emitted by the scintillator strips and guide it to both ends where it is read by multianode photomultiplier tubes. Compared to the OPERA Target Tracker, the JUNO Top Tracker uses new electronics able to cope with the high rate produced by the high rock radioactivity compared to the one in Gran Sasso underground laboratory. This paper will present the new electronics and mechanical structure developed for the Top Tracker of JUNO along with its expected performance based on the current detector simulation.

Abstract The physics potential of detecting 8 B solar neutrinos will be exploited at the Jiangmen Underground Neutrino Observatory (JUNO), in a model-independent manner by using three distinct channels of the charged current (CC), neutral current (NC), and elastic scattering (ES) interactions. Due to the largest-ever mass of 13 C nuclei in the liquid scintillator detectors and the expected low background level, 8 B solar neutrinos are observable in the CC and NC interactions on 13 C for the first time. By virtue of optimized event selections and muon veto strategies, backgrounds from the accidental coincidence, muon-induced isotopes, and external backgrounds can be greatly suppressed. Excellent signal-to-background ratios can be achieved in the CC, NC, and ES channels to guarantee the observation of the 8 B solar neutrinos. From the sensitivity studies performed in this work, we show that JUNO, with 10 yr of data, can reach the 1 σ precision levels of 5%, 8%, and 20% for the 8 B neutrino flux, <?CDATA ${\sin }^{2}{\theta }_{12}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>sin</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:msub> <mml:mrow> <mml:mi>θ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>12</mml:mn> </mml:mrow> </mml:msub> </mml:math> , and <?CDATA ${\rm{\Delta }}{m}_{21}^{2}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:msubsup> <mml:mrow> <mml:mi>m</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>21</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , respectively. Probing the details of both solar physics and neutrino physics would be unique and helpful. In addition, when combined with the Sudbury Neutrino Observatory measurement, the world's best precision of 3% is expected for the measurement of the 8 B neutrino flux.

We present the first measurement of the induced proton polarization P_n in pi^0 electroproduction on the proton around the Delta resonance. The measurement was made at a central invariant mass and a squared four-momentum transfer of W=1231 MeV and Q^2 = 0.126 (GeV/c)^2, respectively. We measured a large induced polarization, P_n = -0.397 +/- 0.055 +/- 0.009. The data suggest that the scalar background is larger than expected from a recent effective Hamiltonian model.

We report on the first measurement of exclusive Xi-(1321) hyperon photoproduction in gamma p --> K+ K+ Xi- for 3.2 < E(gamma) < 3.9 GeV. The final state is identified by the missing mass in p(gamma,K+ K+)X measured with the CLAS detector at Jefferson Laboratory. We have detected a significant number of the ground-state Xi-(1321)1/2+, and have estimated the total cross section for its production. We have also observed the first excited state Xi-(1530)3/2+. Photoproduction provides a copious source of Xi's. We discuss the possibilities of a search for the recently proposed Xi5-- and Xi5+ pentaquarks.

Received 30 March 2006DOI:https://doi.org/10.1103/PhysRevLett.96.169905©2006 American Physical Society

A bstract We study damping signatures at the Jiangmen Underground Neutrino Observatory (JUNO), a medium-baseline reactor neutrino oscillation experiment. These damping signatures are motivated by various new physics models, including quantum decoherence, ν 3 decay, neutrino absorption, and wave packet decoherence. The phenomenological effects of these models can be characterized by exponential damping factors at the probability level. We assess how well JUNO can constrain these damping parameters and how to disentangle these different damping signatures at JUNO. Compared to current experimental limits, JUNO can significantly improve the limits on τ 3 / m 3 in the ν 3 decay model, the width of the neutrino wave packet σ x , and the intrinsic relative dispersion of neutrino momentum σ rel .

The reaction $ep \to e'K^+\Lambda(1520)$ with $\Lambda(1520) \to p'K^-$ was studied at electron beam energies of 4.05, 4.25, and 4.46 GeV, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cos$\theta_{K^+}$, $\phi_{K^+}$, $Q^2$, and $W$ dependencies of $\Lambda$(1520) electroproduction are presented for the kinematic region 0.9 $<$ $Q^2$ $<$ 2.4 GeV$^2$ and 1.95 $<$ $W$ $<$ 2.65 GeV. Also, the $Q^2$ dependence of the $\Lambda$(1520) decay angular distribution is presented for the first time. The cos$\theta_{K^+}$ angular distributions suggest {\it t}-channel diagrams dominate the production process. Fits to the $\Lambda$(1520) {\it t}-channel helicity frame decay angular distributions indicate the $m_{z}=\pm{1/2}$ parentage accounts for about 60% of the total yield, which suggests this reaction has a significant contribution from {\it t}-channel processes with either K$^+$ exchange or longitudinal coupling to an exchanged K$^*$. The $Q^2$ dependence of the $\Lambda$(1520) production cross section is the same as that observed for $\Lambda$(1116) photo- and electroproduction.

Inclusive electron scattering off the deuteron has been measured to extract the deuteron structure function ${F}_{2}$ with the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement covers the entire resonance region from the quasielastic peak up to the invariant mass of the final-state hadronic system $W\ensuremath{\simeq}2.7$ GeV with four-momentum transfers ${Q}^{2}$ from $0.4$ to 6 (GeV/c)${}^{2}$. These data are complementary to previous measurements of the proton structure function ${F}_{2}$ and cover a similar two-dimensional region of ${Q}^{2}$ and Bjorken variable x. Determination of the deuteron ${F}_{2}$ over a large x interval including the quasielastic peak as a function of ${Q}^{2}$, together with the other world data, permit a direct evaluation of the structure function moments for the first time. By fitting the ${Q}^{2}$ evolution of these moments with an OPE-based twist expansion we have obtained a separation of the leading twist and higher twist terms. The observed ${Q}^{2}$ behavior of the higher twist contribution suggests a partial cancelation of different higher twists entering into the expansion with opposite signs. This cancelation, found also in the proton moments, is a manifestation of the ``duality'' phenomenon in the ${F}_{2}$ structure function.

Two-proton correlations at small relative momentum q were studied in the eA( 3 He, 4 He, C, Fe)→ e ′ ppX reaction at E 0 = 4.46 GeV using the CLAS detector at Jefferson Lab.The enhancement of the correlation function at small q was found to be in accordance with theoretical expectation.Emission region sizes were extracted and proved to be dependent on A and proton momentum.The size of the two-proton emission region on the lightest possible nucleus, He, was measured for the first time.

The three-body photodisintegration of $^{3}\mathrm{He}$ has been measured with the CLAS detector at Jefferson Lab, using tagged photons of energies between $0.35$ GeV and $1.55\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$. The large acceptance of the spectrometer allowed us for the first time to cover a wide momentum and angular range for the two outgoing protons. Three kinematic regions dominated by either two- or three-body contributions have been distinguished and analyzed. The measured cross sections have been compared with results of a theoretical model, which, in certain kinematic ranges, have been found to be in reasonable agreement with the data.

Measurements of the angular distributions of target and double spin asymmetries for the Delta(1232) in the exclusive channel (polarized-p polarized-e,e-prime p)pi0 obtained at Jefferson Lab in the Q2 range from 0.5 to 1.5 gev2 are presented. Results of the asymmetries are compared with the unitary isobar model, dynamical models, and the effective Lagrangian theory. Sensitivity to the different models was observed, particularly in relation to the description of background terms on which the target asymmetry depends significantly.

The polarized longitudinal-transverse structure function $\sigma_{LT^\prime}$ measures the interference between real and imaginary amplitudes in pion electroproduction and can be used to probe the coupling between resonant and non-resonant processes. We report new measurements of $\sigma_{LT^\prime}$ in the $N(1440){1/2}^+$ (Roper) resonance region at $Q^2=0.40$ and 0.65 GeV$^2$ for both the $\pi^0 p$ and $\pi^+ n$ channels. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at a beam energy of 1.515 GeV. Complete angular distributions were obtained and are compared to recent phenomenological models. The $\sigma_{LT^\prime}(\pi^+ n)$ channel shows a large sensitivity to the Roper resonance multipoles $M_{1-}$ and $S_{1-}$ and provides new constraints on models of resonance formation.

The double spin asymmetry in the $\stackrel{\ensuremath{\rightarrow}}{e}\stackrel{\ensuremath{\rightarrow}}{p}\ensuremath{\rightarrow}{e}^{\ensuremath{'}}{\ensuremath{\pi}}^{+}n$ reaction has been measured for the first time in the resonance region for four-momentum transfer ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.35--1.5{\mathrm{GeV}}^{2}$. Data were taken at Jefferson Lab with the CLAS detector using a 2.6 GeV polarized electron beam incident on a polarized solid ${\mathrm{NH}}_{3}$ target. Comparison with predictions of phenomenological models shows strong sensitivity to resonance contributions. Helicity- $1/2$ transitions are found to be dominant in the second and third resonance regions. The measured asymmetry is consistent with a faster rise with ${Q}^{2}$ of the helicity asymmetry ${A}_{1}$ for the ${F}_{15}(1680)$ resonance than expected from the analysis of the unpolarized data.

We studied the exclusive reaction e p --> e' p' phi using the phi --> K^+ K^- decay mode. The data were collected using a 4.2 GeV incident electron beam and the CLAS detector at Jefferson Lab. Our experiment covers the range in Q^2 from 0.7 to 2.2 GeV^2, and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of phi production on the proton. Our measurement shows the expected decrease of the t-slope with the vector meson formation time c Delta tau below 2 fm. At = 0.6 fm, we measure b_phi = 2.27 +- 0.42 GeV^-2. The cross section dependence on W as W^{0.2+-0.1} at Q^2 = 1.3 GeV^2 was determined by comparison with phi production at HERA after correcting for threshold effects. This is the same dependence as observed in photoproduction.

As part of a measurement of the cross section of $\phi$ meson photoproduction to high momentum transfer, we measured the polar angular decay distribution of the outgoing $K^+$ in the channel $\phi \to K^+K^-$ in the $\phi$ center-of-mass frame (the helicity frame). We find that s-channel helicity conservation (SCHC) holds in the kinematical range where $t$-channel exchange dominates (up to $-t \sim 2.5$ GeV$^2$ for $E_{\gamma}$=3.6 GeV). Above this momentum, $u$-channel production of a $\phi$ meson dominates and induces a violation of SCHC. The deduced value of the $\phi NN$ coupling constant lies in the upper range of previously reported values.

Cross sections were measured for the near-threshold electrodisintegration of 3He at momentum transfer values of q=2.4, 4.4, and 4.7fm−1. From these and prior measurements the transverse and longitudinal response functions RT and RL were deduced. Comparisons are made against previously published and new nonrelativistic A=3 calculations using the best available nucleon-nucleon NN potentials. In general, for q<2fm−1 these calculations accurately predict the threshold electrodisintegration of 3He. Agreement at increasing q demands consideration of two-body terms, but discrepancies still appear at the highest momentum transfers probed, perhaps due to the neglect of relativistic dynamics, or to the underestimation of high-momentum wave-function components.Received 10 March 2003DOI:https://doi.org/10.1103/PhysRevC.67.064004©2003 American Physical Society

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation B. Asavapibhop, N. Suwonjandee; Loop‐the‐Loop: An Easy Experiment, A Challenging Explanation. AIP Conf. Proc. 28 July 2010; 1263 (1): 249–251. https://doi.org/10.1063/1.3479881 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

During the Thai high-school physics teacher training programme, we used an aluminum loop-the-loop system built by the Institute for the Promotion of Teaching Science and Technology (IPST) to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. There were 27 high-school teachers from three provinces, Bangkok, Ra-yong and Phuket. A steel ball was released at a certain height and then moved into the circular loop and underwent a projectile motion upon leaving the track. We asked the teachers to predict the landing position of the ball if we changed the height of the whole loop-the-loop system. We analysed the methods they used to determine their answers. It turned out that most teachers could not get the correct landing position of the ball. Some did not realize the effect of the friction between the ball and the track. Some did not realize the similar condition of the loop-the-loop system before and after it was moved up by a certain distance. Only a few teachers did realize this and got the correct answers.

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton LS detector at 700-m underground. An excellent energy resolution and a large fiducial volume offer exciting opportunities for addressing many important topics in neutrino and astro-particle physics. With 6 years of data, the neutrino mass ordering can be determined at 3-4 sigma and three oscillation parameters can be measured to a precision of 0.6% or better by detecting reactor antineutrinos. With 10 years of data, DSNB could be observed at 3-sigma; a lower limit of the proton lifetime of 8.34e33 years (90% C.L.) can be set by searching for p->nu_bar K^+; detection of solar neutrinos would shed new light on the solar metallicity problem and examine the vacuum-matter transition region. A core-collapse supernova at 10 kpc would lead to ~5000 IBD and ~2000 (300) all-flavor neutrino-proton (electron) scattering events. Geo-neutrinos can be detected with a rate of ~400 events/year. We also summarize the final design of the JUNO detector and the key R&D achievements. All 20-inch PMTs have been tested. The average photon detection efficiency is 28.9% for the 15,000 MCP PMTs and 28.1% for the 5,000 dynode PMTs, higher than the JUNO requirement of 27%. Together with the >20 m attenuation length of LS, we expect a yield of 1345 p.e. per MeV and an effective energy resolution of 3.02%/\sqrt{E (MeV)}$ in simulations. The underwater electronics is designed to have a loss rate <0.5% in 6 years. With degassing membranes and a micro-bubble system, the radon concentration in the 35-kton water pool could be lowered to <10 mBq/m^3. Acrylic panels of radiopurity <0.5 ppt U/Th are produced. The 20-kton LS will be purified onsite. Singles in the fiducial volume can be controlled to ~10 Hz. The JUNO experiment also features a double calorimeter system with 25,600 3-inch PMTs, a LS testing facility OSIRIS, and a near detector TAO.

We study damping signatures at the Jiangmen Underground Neutrino Observatory (JUNO), a medium-baseline reactor neutrino oscillation experiment. These damping signatures are motivated by various new physics models, including quantum decoherence, $\nu_3$ decay, neutrino absorption, and wave packet decoherence. The phenomenological effects of these models can be characterized by exponential damping factors at the probability level. We assess how well JUNO can constrain these damping parameters and how to disentangle these different damping signatures at JUNO. Compared to current experimental limits, JUNO can significantly improve the limits on $\tau_3/m_3$ in the $\nu_3$ decay model, the width of the neutrino wave packet $\sigma_x$, and the intrinsic relative dispersion of neutrino momentum $\sigma_{\rm rel}$.

New electron scattering measurements have been made that extend data on the ${}^{3}\mathrm{He}$ elastic magnetic form factor up to ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}42.6{\mathrm{fm}}^{\ensuremath{-}2}$. These new data test theoretical conjectures regarding non-nucleonic effects in the three-body system. The very small cross sections, as low as ${10}^{\ensuremath{-}40}{\mathrm{cm}}^{2}/\mathrm{sr}$, required the use of a high-pressure cryogenic gas target and a detector system with excellent background rejection capability. No existing theoretical calculation satisfactorily accounts for all the available data.

We studied the exclusive reaction ep→eЈpЈ using the →K ϩ K Ϫ decay mode.The data were collected using a 4.2 GeV incident electron beam and the CEBAF Large Acceptance Spectrometer ͑CLAS͒ at the Thomas Jefferson National Accelerator Facility.Our experiment covers the range in Q 2 from 0.7 to 2.2 GeV 2 , and W from 2.0 to 2.6 GeV.Taken together with all previous data, we find a consistent picture of production on the proton.Our measurement shows the expected decrease of the t slope with the vector-meson formation time c⌬ below 2 fm.At ͗c⌬͘ϭ0.6 fm, we measure b ϭ2.27Ϯ0.42GeV Ϫ2 .The cross section dependence on W as W 0.2Ϯ0.1 at Q 2 ϭ1.3 GeV 2 was determined by comparison with production at HERA after correcting for threshold effects.This is the same dependence as observed in photoproduction.

Received 19 November 2002DOI:https://doi.org/10.1103/PhysRevLett.89.249904©2002 American Physical Society

The electromagnetic decays of the Sig0(1385) and Lambda(1520) hyperons were studied in photon-induced reactions gamma p -> K+ Lambda(1116)gamma in the CLAS detector at the Thomas Jefferson National Accelerator Facility. We report the first observation of the radiative decay of the Sig0(1385) and a measurement of the Lambda(1520) radiative decay width. For the Sig0(1385) -> Lambda(1116)gamma transition, we measured a partial width of 479+/-120(stat)+81-100(sys) keV, larger than all of the existing model predictions. For the Lambda(1520) -> Lambda(1116)gamma transition, we obtained a partial width of 167+/-43(stat)+26-12(sys) keV.

The Colorado Learning Attitudes about Science Survey, CLASS, has been used as a tool to measure respondents' beliefs or attitudes about physics and how they learn physics. It is composed of 42 Likert scale (strongly disagree to strongly agree) type questions which is classified into 8 categories, which are real world connections, conceptual connections, personal interest, sense making, applied conceptual understanding, problem solving general, problem solving confidence and problem solving sophistication. In this study, we asked 196 high school physics teachers and 211 students from 195 secondary schools in Thailand to respond to this survey along with a 6-open-ended-question survey. In this paper, we focus on two topics: "What is the difficulty in learning/teaching physics?" and "What is the goal in learning/teaching physics?" We found that physics teachers agree with the experts in most categories, except conceptual connections, applied conceptual understanding and problem solving sophistication. While students tend to disagree with the experts in both conceptual categories and all 3 categories in problem solving. We then compare teachers' to students' responses from these two open-ended questions. On the difficulty aspect: 19% of students believe that difficulty in learning physics is due to incomprehension of physics concept. While 43% of teachers thought that difficulty in teaching physics is because of insufficiency of mathematics background. On the goals aspect, 37% of students aim to enter the university; while 50% of teachers target on helping student to better understand physics.

Single spin azimuthal asymmetries A_LT' were measured at Jefferson Lab using 2.2 and 4.4 GeV longitudinally polarized electrons incident on He4 and C12 targets in the CLAS detector. A_LT' is related to the imaginary part of the longitudinal-transverse interference and in quasifree nucleon knockout it provides an unambiguous signature for final state interactions (FSI). Experimental values of A_LT' were found to be below 5%, typically |A_LT'| < 3% for data with good statistical precision. Optical Model in Eikonal Approximation (OMEA) and Relativistic Multiple-Scattering Glauber Approximation (RMSGA) calculations are shown to be consistent with the measured asymmetries.

The Jiangmen Underground Neutrino Observatory (JUNO), the first multi-kton liquid scintillator detector, which is under construction in China, will have a unique potential to perform a real-time measurement of solar neutrinos well below the few MeV threshold typical for Water Cherenkov detectors. JUNO's large target mass and excellent energy resolution are prerequisites for reaching unprecedented levels of precision. In this paper, we provide estimation of the JUNO sensitivity to 7Be, pep, and CNO solar neutrinos that can be obtained via a spectral analysis above the 0.45 MeV threshold. This study is performed assuming different scenarios of the liquid scintillator radiopurity, ranging from the most opti mistic one corresponding to the radiopurity levels obtained by the Borexino experiment, up to the minimum requirements needed to perform the neutrino mass ordering determination with reactor antineutrinos - the main goal of JUNO. Our study shows that in most scenarios, JUNO will be able to improve the current best measurements on 7Be, pep, and CNO solar neutrino fluxes. We also perform a study on the JUNO capability to detect periodical time variations in the solar neutrino flux, such as the day-night modulation induced by neutrino flavor regeneration in Earth, and the modulations induced by temperature changes driven by helioseismic waves.

We discuss JUNO sensitivity to the annihilation of MeV dark matter in the galactic halo via detecting inverse beta decay reactions of electron anti-neutrinos resulting from the annihilation. We study possible backgrounds to the signature, including the reactor neutrinos, diffuse supernova neutrino background, charged- and neutral-current interactions of atmospheric neutrinos, backgrounds from muon-induced fast neutrons and cosmogenic isotopes. A fiducial volume cut, as well as the pulse shape discrimination and the muon veto are applied to suppress the above backgrounds. It is shown that JUNO sensitivity to the thermally averaged dark matter annihilation rate in 10 years of exposure would be significantly better than the present-day best limit set by Super-Kamiokande and would be comparable to that expected by Hyper-Kamiokande.

Abstract We discuss JUNO sensitivity to the annihilation of MeV dark matter in the galactic halo via detecting inverse beta decay reactions of electron anti-neutrinos resulting from the annihilation. We study possible backgrounds to the signature, including the reactor neutrinos, diffuse supernova neutrino background, charged- and neutral-current interactions of atmospheric neutrinos, backgrounds from muon-induced fast neutrons and cosmogenic isotopes. A fiducial volume cut, as well as the pulse shape discrimination and the muon veto are applied to suppress the above backgrounds. It is shown that JUNO sensitivity to the thermally averaged dark matter annihilation rate in 10 years of exposure would be significantly better than the present-day best limit set by Super-Kamiokande and would be comparable to that expected by Hyper-Kamiokande.

Received 15 March 2002DOI:https://doi.org/10.1103/PhysRevLett.88.189903©2002 American Physical Society

The physics potential of detecting $^8$B solar neutrinos will be exploited at the Jiangmen Underground Neutrino Observatory (JUNO), in a model independent manner by using three distinct channels of the charged-current (CC), neutral-current (NC) and elastic scattering (ES) interactions. Due to the largest-ever mass of $^{13}$C nuclei in the liquid-scintillator detectors and the {expected} low background level, $^8$B solar neutrinos would be observable in the CC and NC interactions on $^{13}$C for the first time. By virtue of optimized event selections and muon veto strategies, backgrounds from the accidental coincidence, muon-induced isotopes, and external backgrounds can be greatly suppressed. Excellent signal-to-background ratios can be achieved in the CC, NC and ES channels to guarantee the $^8$B solar neutrino observation. From the sensitivity studies performed in this work, we show that JUNO, with ten years of data, can reach the {1$\sigma$} precision levels of 5%, 8% and 20% for the $^8$B neutrino flux, $\sin^2\theta_{12}$, and $\Delta m^2_{21}$, respectively. It would be unique and helpful to probe the details of both solar physics and neutrino physics. In addition, when combined with SNO, the world-best precision of 3% is expected for the $^8$B neutrino flux measurement.

Supersymmetry proposes that for each Standard Model fermion there exists a boson superpartner and each Standard Model boson has a fermion superpartner. Once new particles are discovered, e.g. at the Large Hadron Collider, a crucial question will be if these will be the supersymmetric partners of the Standard Model particles with the correct spin, i.e. spin-0 for the partners of the fermions. Hence, the spin of these new particles has to be investigated. In this paper, we present a study on the angular correlations of the products from sparticle decay chains via the neutralino, at √s = 14 TeV in pp collisions. Three mSUGRA benchmark points are used as examples to compare the different characteristics of the decay chain of interest. The effects of the spin can be seen through the invariant mass distributions of outgoing leptons and quark. An event selection for the study is proposed and is applied to the inclusive SUSY event samples simulated using fast detector simulation.

The Jiangmen Underground Neutrino Observatory (JUNO) is a neutrino experiment consisting of 2 systems; central detector (CD) and veto systems. The CD is composed of thousands of photomultiplier tubes (PMTs) used to detect light signals from neutrino induced interactions with liquid scintillator inside the CD. Another set of PMTs is used as water Cherenkov detector, together with muon top tracker forming the veto system for background rejection [1]. However, the PMTs' efficiency decreases when they are used in magnetic field. At JUNO's construction site, the Earth Magnetic Field (EMF) is approximately 0.45 G [2]. Therefore, the PMTs of JUNO detector are necessary to be shielded from the EMF.

To maximize the light yield of the liquid scintillator (LS) for the Jiangmen Underground Neutrino Observatory (JUNO), a 20 t LS sample was produced in a pilot plant at Daya Bay. The optical properties of the new LS in various compositions were studied by replacing the gadolinium-loaded LS in one antineutrino detector. The concentrations of the fluor, PPO, and the wavelength shifter, bis-MSB, were increased in 12 steps from 0.5 g/L and <0.01 mg/L to 4 g/L and 13 mg/L, respectively. The numbers of total detected photoelectrons suggest that, with the optically purified solvent, the bis-MSB concentration does not need to be more than 4 mg/L. To bridge the one order of magnitude in the detector size difference between Daya Bay and JUNO, the Daya Bay data were used to tune the parameters of a newly developed optical model. Then, the model and tuned parameters were used in the JUNO simulation. This enabled to determine the optimal composition for the JUNO LS: purified solvent LAB with 2.5 g/L PPO, and 1 to 4 mg/L bis-MSB.

JUNO is a multi-purpose underground neutrino observatory being constructed in the south of China.The main detector, with a 20 kton liquid scintillator target instrumented with about 18k 20" PMT and about 26k 3" PMT, will be strategically located 53 km from the Taishan and Yangjiang Nuclear Power Plants.Using reactor antineutrinos, JUNO will be able to measure several neutrino oscillation parameters with sub-percent precision as well as to determine the neutrino mass ordering to ∼3 over 6 years of operation.Furthermore, JUNO will have a broad physics program, ranging from studying neutrinos from other sources, such as solar and supernova neutrinos, to searching for BSM physics such as proton decay.This talk will give an overview on the JUNO's broad physics potential.

Atmospheric neutrinos are one of the most relevant natural neutrino sources that can be exploited to infer properties about Cosmic Rays and neutrino oscillations. The Jiangmen Underground Neutrino Observatory (JUNO) experiment, a 20 kton liquid scintillator detector with excellent energy resolution is currently under construction in China. JUNO will be able to detect several atmospheric neutrinos per day given the large volume. A study on the JUNO detection and reconstruction capabilities of atmospheric $\nu_e$ and $\nu_\mu$ fluxes is presented in this paper. In this study, a sample of atmospheric neutrinos Monte Carlo events has been generated, starting from theoretical models, and then processed by the detector simulation. The excellent timing resolution of the 3 PMT light detection system of JUNO detector and the much higher light yield for scintillation over Cherenkov allow to measure the time structure of the scintillation light with very high precision. Since $\nu_e$ and $\nu_\mu$ interactions produce a slightly different light pattern, the different time evolution of light allows to discriminate the flavor of primary neutrinos. A probabilistic unfolding method has been used, in order to infer the primary neutrino energy spectrum from the detector experimental observables. The simulated spectrum has been reconstructed between 100 MeV and 10 GeV, showing a great potential of the detector in the atmospheric low energy region.

The observation of a new particle with a mass of about 125 GeV, announced in July 2012 by the ATLAS and CMS collaborations, has given hope to the HEP community that the long sought Higgs boson, the last missing ingredient of the Standard Model of Particle Physics, might have been discovered at last. The Compact Muon Solenoid experiment (CMS) is a general-purpose detector installed at the Large Hadron Collider (LHC) at CERN. During 2011 and 2012, the CMS detector has collected over 17 inverse femto-barns of proton-proton collisions (5 fb -1 at √s=7 TeV and 12 fb -1 at √s=8 TeV). These data are currently been analyzed to further characterize the recently discovered Higgs boson candidate. For a Higgs mass of about 125 GeV, the dominant decay mode should be into bb - ; however, such decay has not yet been observed experimentally due to overwhelming backgrounds. A promising channel to search for H→bb - is the VHbb channel, where the Higgs boson is produced via the 'Higgs-Strahlung' process (a virtual W or Z boson with sufficient energy can then emit a Higgs) and recoils with large momentum transverse to the beam-line, to finally decay into a bb - pair (b-jets). The presence of a vector boson in the final state highly suppresses the large QCD background and provides an efficient trigger path when the vector boson decays to charged leptons (e, μ). Recent developments in τ lepton reconstruction and vector boson invariant mass determination made it feasible to extend the VHbb analysis to both leptonic (e, μ) and hadronic (jets) decays of the τ lepton. The current VHbb results are summarized and the novel VHbb final states are presented, with particular focus on HZ, with H decaying to b-quarks and Z decaying to tau electron and hadronic tau.

The measurement of alpha scattering from gold was instrumental in developing the model of an atom. Rutherford was able to verify this model by predicting the number of particles scattering at each angle. The Rutherford scattering cross sections were studied using the Geant4 (Geometry and tracking) software. Most of the results from the simulation were found to correspond with the data calculated using the Rutherford scattering formula. The trajectories of alpha particles produced during the reaction could be visualized through the simulation. This research showed that Geant4 can simulate accurately the scattering of charged particles from materials. Moreover, Geant4 can be applied in the simulation of the scattering of other particles from different materials in an elastic collision. The simulation by Geant4 is also beneficial in the physics laboratory since it can assist students in their understanding of Rutherford’s alpha scattering experiments and avoid any unnecessary exposure to radioactive

We report measurements of the beam spin asymmetry in Deeply Virtual Compton Scattering (DVCS) at an electron beam energy of $4.8$ GeV using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The DVCS beam spin asymmetry has been measured in a wide range of kinematics, $1$(GeV/c)$^2$ $

JUNO is a multi-purpose neutrino observatory under construction in the south of China. This publication presents new sensitivity estimates for the measurement of the $\Delta m^2_{31}$, $\Delta m^2_{21}$, $\sin^2 \theta_{12}$, and $\sin^2 \theta_{13}$ oscillation parameters using reactor antineutrinos, which is one of the primary physics goals of the experiment. The sensitivities are obtained using the best knowledge available to date on the location and overburden of the experimental site, the nuclear reactors in the surrounding area and beyond, the detector response uncertainties, and the reactor antineutrino spectral shape constraints expected from the TAO satellite detector. It is found that the $\Delta m^2_{31}$, $\Delta m^2_{21}$, and $\sin^2 \theta_{12}$ oscillation parameters will be determined to better than 0.5% precision in six years of data collection, which represents approximately an order of magnitude improvement over existing constraints.

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel.

Cosmic ray, originating from several galactic sources, bombards the Earth's atmosphere and produces lots of secondary particles. One of them is an unstable charged particle known as "muon" (μ±) with speed close to speed of light and lifetime about 2.2 microseconds before decaying into others. In this study, a spark chamber detector with a stack of 10 parallel electrode plates is constructed to detect the cosmic-ray muons which will lose their energies via ionization in the helium filled chamber. When muons passing through the chamber, they left their traces as the ionization paths. Sparks will occur immediately between each stack of parallel electrodes which are connected to a high voltage supply. The muon's trajectory can then be visualized by connecting the sparks in each stack. To construct this muon's path, two cameras are set to record the events from the two perpendicular planes on two sides of the chamber. The photos are analyzed using MATLAB to obtain the coordinates of the sparking tracks which then are used to determine the zenith angular distribution. The results show that a large number of muons arrived at our laboratory (Chulalongkorn University, Bangkok, Thailand 13° 44'09.5"N 100°31'49.6"E) with zenith angle about 30°

In Particle Data Analysis laboratory activity, aimed at undergraduate and high school students, the student is tasked with classifying collision events which contain two muons decaying from J/ψ meson. The activity provides 2000 collision events from the CMS detector, selected by CMS outreach community. However, classifying 2000 collision events by hand can be a tedious task for any human, so a smaller subset of collision events are usually used in the activity to save time. We built a machine learning classifier which mimic the student's classification based on a subset of collision events handed to the student, using some information from data in corresponding collision event. The information used in this system is parts of muon trajectory, extracted from files suited for CMS event viewer on the internet, as well as the four-momentum of both muons, available from the same source. With this system, students can input a subset of graded events into the system, and the system will be able to illustrate the results if the student worked on all 2000 collision events using his/her logic. Users can download the code from our repository and follow easy instructions to replicate this activity.

The Jiangmen Underground Neutrino Observatory~(JUNO) features a 20~kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent experiment for $^8$B solar neutrino measurements, such as its low-energy threshold, its high energy resolution compared to water Cherenkov detectors, and its much large target mass compared to previous liquid scintillator detectors. In this paper we present a comprehensive assessment of JUNO's potential for detecting $^8$B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2~MeV threshold on the recoil electron energy is found to be achievable assuming the intrinsic radioactive background $^{238}$U and $^{232}$Th in the liquid scintillator can be controlled to 10$^{-17}$~g/g. With ten years of data taking, about 60,000 signal and 30,000 background events are expected. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter, which will shed new light on the tension between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework. If $\Delta m^{2}_{21}=4.8\times10^{-5}~(7.5\times10^{-5})$~eV$^{2}$, JUNO can provide evidence of neutrino oscillation in the Earth at the about 3$\sigma$~(2$\sigma$) level by measuring the non-zero signal rate variation with respect to the solar zenith angle. Moveover, JUNO can simultaneously measure $\Delta m^2_{21}$ using $^8$B solar neutrinos to a precision of 20\% or better depending on the central value and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help elucidate the current tension between the value of $\Delta m^2_{21}$ reported by solar neutrino experiments and the KamLAND experiment.