S. Dugad

We describe the design, construction and performance of the upgraded DO muon system for Run II of the Fermilab Tevatron collider. Significant improvements have been made to the major subsystems of the DO muon detector: trigger scintillation counters, tracking detectors, and electronics. The Run II central muon detector has a new scintillation counter system inside the iron toroid and an improved scintillation counter system outside the iron toroid. In the forward region, new scintillation counter and tracking systems have been installed. Extensive shielding has been added in the forward region. A large fraction of the muon system electronics is also new.

The D0 collaboration has performed a measurement of the top quark mass based on six candidate events for the process t tbar -> b W+ bbar W-, where the W bosons decay to e nu or mu nu. This sample was collected during an exposure of the D0 detector to an integrated luminosity of 125 pb^-1 of sqrt(s)=1.8 TeV p-pbar collisions. We obtain mt = 168.4 +- 12.3 (stat) +- 3.7 (sys) GeV/c^2, consistent with the measurement obtained using single-lepton events. Combination of the single-lepton and dilepton results yields mt = 172.0 +- 7.5 GeV/c^2.

We determine the top quark mass mt using tt¯ pairs produced in the DØ detector by s=1.8TeV pp¯ collisions in a 125pb−1 exposure at the Fermilab Tevatron. We make a two constraint fit to mt in tt¯→bW+b¯W− final states with one W boson decaying to qq¯ and the other to eν or μν. Likelihood fits to the data yield mt(l+jets)=173.3±5.6(stat)±5.5(syst) GeV/c2. When this result is combined with an analysis of events in which both W bosons decay into leptons, we obtain mt=172.1±5.2(stat)±4.9(syst) GeV/c2. An alternate analysis, using three constraint fits to fixed top quark masses, gives mt(l+jets)=176.0±7.9(stat)±4.8(syst) GeV/c2, consistent with the above result. Studies of kinematic distributions of the top quark candidates are also presented. 14.65.Ha, 13.85.Ni, 13.85.QkReceived 27 January 1998DOI:https://doi.org/10.1103/PhysRevD.58.052001©1998 American Physical Society

We present the measurement of the cosmic ray proton spectrum from 50 TeV to 1.3 PeV using 7.81×10^{6} extensive air shower events recorded by the ground-based GRAPES-3 experiment between 1 January 2014 and 26 October 2015 with a live time of 460 day. Our measurements provide an overlap with direct observations by satellite and balloon-based experiments. The electromagnetic and muon components in the shower were measured by a dense array of plastic scintillator detectors and a tracking muon telescope, respectively. The relative composition of the proton primary from the air shower data containing all primary particles was extracted using the multiplicity distribution of muons which is a sensitive observable for mass composition. The observed proton spectrum suggests a spectral hardening at ∼166 TeV and disfavors a single power law description of the spectrum up to the Knee energy (∼3 PeV).

We present measurements of the bb production cross section and angular correlations using the DØ detector at the Fermilab Tevatron pp Collider operating at s = 1.8 TeV. The b quark production cross section for |yb|<1.0 and pTb>6 GeV/c is extracted from single muon and dimuon data samples. The results agree in shape with the next-to-leading order QCD calculation of heavy flavor production but are greater than the central values of these predictions. The angular correlations between b and b quarks, measured from the azimuthal opening angle between their decay muons, also agree in shape with the next-to-leading order QCD prediction.

We present a search for events consistent with the production and decay of the squarks and gluinos of the minimal supersymmetric standard model (MSSM) in the D0 detector at the Fermilab Tevatron $p\overline{p}$ collider. We examined data for events containing large missing transverse energy and three or more jets. We observed no excess of events above the expected yield from standard model processes. For a choice of MSSM parameter values, we set a lower limit at the 95% confidence level on the mass of the gluino of 144 GeV ${/c}^{2}$ for all squark masses and a lower limit of 212 GeV ${/c}^{2}$ for equal squark and gluino masses.

We measure the top quark mass m t using t t pairs produced in the DØ detector by √ s = 1.8 TeV pp collisions in a 125 pb -1 exposure at the Fermilab Tevatron.We make a two constraint fit to m t in t t → bW + bW -final states with one W decaying to q q and the other to eν or µν.Events are binned in fit mass versus a measure of probability for events to be signal rather than background.Likelihood fits to the data yield m t = 173.3± 5.6 (stat) ± 6.2 (syst) GeV/c 2 .

We have studied Jψ production in pp collisions at s = 1.8 TeV with the DØ detector at Fermilab using μ+μ− data. We have measured the inclusive Jψ production cross section as a function of Jψ transverse momentum, pT. For the kinematic range pT > 8 GeV/c and |η| < 0.6 we obtain σ(pp → Jψ + X) · Br(Jψ → μ+μ−) = 2.08 ± 0.17(stat) ± 0.46(syst) nb. Using the muon impact parameter we have estimated the fraction of Jψ mesons coming from B meson decays to be fb = 0.35 ± 0.09(stat)±0.10(syst) and inferred the inclusive b production cross section. From the information on the event topology the fraction of nonisolated Jψ events has been measured to be fnonisol = 0.64 ± 0.08(stat)±0.06(syst). We have also obtained the fraction of Jψ events resulting from radiative decays of χc states, fχ = 0.32 ± 0.07(stat)±0.07(syst). We discuss the implications of our measurements for charmonium production processes.

We present a measurement of the inclusive jet cross section in p¯p collisions at √s =1.8 TeV at the Fermilab Tevatron using the Collider Detector at Fermilab. Good agreement is seen with the predictions of recent next-to-leading-order [O(α3s)] QCD predictions. The dependence of the cross section on clustering cone size is reported for the first time. An improved limit on Λc, a term characterizing possible quark substructure, is set at 1.4 TeV (95% C.L.).Received 7 August 1991DOI:https://doi.org/10.1103/PhysRevLett.68.1104©1992 American Physical Society

We report on the test beam results and calibration methods using high energy electrons, pions and muons with the CMS forward calorimeter (HF). The HF calorimeter covers a large pseudorapidity region ( $3\leq|\eta|\leq5$ ), and is essential for a large number of physics channels with missing transverse energy. It is also expected to play a prominent role in the measurement of forward tagging jets in weak boson fusion channels in Higgs production. The HF calorimeter is based on steel absorber with embedded fused-silica-core optical fibers where Cherenkov radiation forms the basis of signal generation. Thus, the detector is essentially sensitive only to the electromagnetic shower core and is highly non-compensating (e/h≈5). This feature is also manifest in narrow and relatively short showers compared to similar calorimeters based on ionization. The choice of fused-silica optical fibers as active material is dictated by its exceptional radiation hardness. The electromagnetic energy resolution is dominated by photoelectron statistics and can be expressed in the customary form as $\frac{a}{\sqrt{E}}\oplus{b}$ . The stochastic term a is 198% and the constant term b is 9%. The hadronic energy resolution is largely determined by the fluctuations in the neutral pion production in showers, and when it is expressed as in the electromagnetic case, a = 280% and b = 11%.

Aims. We seek to identify the primary agents causing Forbush decreases (FDs) in high-rigidity cosmic rays observed from the Earth. In particular, we ask if these FDs are caused mainly by coronal mass ejections (CMEs) from the Sun that are directed towards the Earth, or by their associated shocks.

The GRAPES-3 muon telescope located in Ooty, India records rapid (∼10 min) variations in the muon intensity during major thunderstorms. Out of a total of 184 thunderstorms recorded during the interval of April 2011-December 2014, the one on December 1, 2014 produced a massive potential of 1.3 GV. The electric field measured by four well-separated (up to 6 km) monitors on the ground was used to help estimate some of the properties of this thundercloud, including its altitude and area that were found to be 11.4 km above mean sea level and ≥380 km^{2}, respectively. A charging time of 6 min to reach 1.3 GV implied the delivery of a power of ≥2 GW by this thundercloud that was moving at a speed of ∼60 km h^{-1}. This work possibly provides the first direct evidence for the generation of gigavolt potentials in thunderclouds that could also possibly explain the production of highest-energy (100 MeV) gamma rays in the terrestrial gamma-ray flashes.

Abstract The GRAPES-3 experiment located in Ooty, India, samples the electron and muon components in extensive air showers using an array of plastic scintillator detectors and a muon telescope (G3MT) consisting of proportional counters to study the composition of primary cosmic rays (PCRs) as well as γ -ray sources in the TeV–PeV energy range. The G3MT is designed with an appropriate mass absorber to shield the electromagnetic and hadronic components in the shower and to detect muons above 1 GeV×sec( θ ) energy, incident from a zenith angle θ . We developed a simulation framework based on the GEANT4 toolkit to evaluate the response of shower particles such as muons, γ -rays, electrons and hadrons in the G3MT. We discuss the geometric modeling of the G3MT using GEANT4 starting with the proportional counter. We estimated the punch-through contribution of hadrons in the G3MT. We compare the simulated muon multiplicity distributions with the observed ones assuming PCR composition from a four population supernova remnant acceleration model namely H4a.

We present a search for charged Higgs bosons in decays of pair-produced top quarks using $109.2\ifmmode\pm\else\textpm\fi{}5.8{\mathrm{pb}}^{\ensuremath{-}1}$ of data recorded from $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ by the D0 detector during 1992--1996 at the Fermilab Tevatron. No evidence is found for charged Higgs production, and most parts of the $[{M}_{{H}^{+}},\mathrm{tan}\ensuremath{\beta}]$ parameter space where the decay $t\ensuremath{\rightarrow}{H}^{+}b$ has a branching fraction close to or larger than that for $t\ensuremath{\rightarrow}{W}^{+}b$ are excluded at $95%$ confidence level. Assuming ${m}_{t}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}175\mathrm{GeV}$ and $\ensuremath{\sigma}(p\overline{p}\ensuremath{\rightarrow}t\overline{t})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5.5\mathrm{pb}$, for ${M}_{{H}^{+}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}60\mathrm{GeV}$, we exclude $\mathrm{tan}\ensuremath{\beta}&lt;0.97$ and $\mathrm{tan}\ensuremath{\beta}&gt;40.9$.

We report a measurement of the top quark mass using six candidate events for the process $p\overline{p}\ensuremath{\rightarrow}t\overline{t}+\stackrel{\ensuremath{\rightarrow}}{X}{l}^{+}\ensuremath{\nu}{\mathrm{bl}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}\overline{b}+X$, observed in the D0 experiment at the Fermilab $p\overline{p}$ collider. Using maximum likelihood fits to the dynamics of the decays, we measure a mass for the top quark of ${m}_{t}=168.4\ifmmode\pm\else\textpm\fi{}12.3(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}3.6(\mathrm{syst}) \mathrm{Gev}$. We combine this result with our previous measurement in the $t\overline{t}\ensuremath{\rightarrow}l+\mathrm{jets}$ channel to obtain ${m}_{t}=172.1\ifmmode\pm\else\textpm\fi{}7.1 \mathrm{GeV}$ as the best value of the mass of the top quark measured by D0.

We present a search for pair produced top squarks, the supersymmetric partners of the top quark, using the D0 detector at the Fermilab Tevatron $p\overline{p}$ collider. We consider a scenario in which the lighter of the two top squarks ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{t}}_{1}$ decays with 100% branching fraction to a charm quark and the lightest neutralino ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}$ yielding a signal of two acollinear jets with missing transverse energy. We observe 3 events while we expect $3.5\ifmmode\pm\else\textpm\fi{}1.2$ events from the known standard model processes. We exclude at the 95% confidence level a significant region of the ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{t}}_{1}}$- ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}}$ parameter space. The highest ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{t}}_{1}}$ value we exclude is $93\mathrm{GeV}{/c}^{2}$ with a corresponding ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}}$ value of $8\mathrm{G}\mathrm{e}\mathrm{V}/{c}^{2}$.

We report a new measurement of the pseudorapidity (eta) and transverse-energy ( E(T)) dependence of the inclusive jet production cross section in pp(macro) collisions at square root of s = 1.8 TeV using 95 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron. The differential cross section d(2)sigma/(dE(T)d eta) is presented up to eta = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD and indicate a preference for certain parton distribution functions.

We present results on the search for the top quark in pp\ifmmode\bar\else\textasciimacron\fi{} collisions at \ensuremath{\surd}s =1.8 TeV with an integrated luminosity of 13.5\ifmmode\pm\else\textpm\fi{}1.6 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$. We have considered tt\ifmmode\bar\else\textasciimacron\fi{} production in the standard model using electron and muon dilepton decay channels (tt\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}e\ensuremath{\mu}+jets, ee+jets, and \ensuremath{\mu}\ensuremath{\mu}+jets) and single-lepton decay channels (tt\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}e+jets and \ensuremath{\mu}+jets) with and without tagging of b quark jets. An analysis of these data optimized for top quark masses below 140 GeV/${\mathit{c}}^{2}$ gives a lower top quark mass limit of 128 GeV/${\mathit{c}}^{2}$. An analysis optimized for higher top quark masses yields 9 events with an expected background of 3.8\ifmmode\pm\else\textpm\fi{}0.9. If we assume that the excess is due to tt\ifmmode\bar\else\textasciimacron\fi{} production, and assuming a top quark mass of 180 GeV/${\mathit{c}}^{2}$, we obtain a cross section of 8.2\ifmmode\pm\else\textpm\fi{}5.1 pb.

We report a new measurement of the cross section for the production of isolated photons with transverse energies ( E(gamma)(T)) above 10 GeV and pseudorapidities |eta|<2.5 in p&pmacr; collisions at sqrt[s] = 1.8 TeV. The results are based on a data sample of 107.6 pb(-1) recorded during 1992-1995 with the D0 detector at the Fermilab Tevatron collider. The background, predominantly from jets which fragment to neutral mesons, was estimated using the longitudinal shower shape of photon candidates in the calorimeter. The measured cross section is in good agreement with the next-to-leading order QCD calculation for E(gamma)(T) greater, similar36 GeV.

Aims. Forbush decrease (FD) is a transient decrease followed by a gradual recovery in the observed galactic cosmic ray intensity. We seek to understand the relationship between the FDs and near-Earth interplanetary magnetic field (IMF) enhancements associated with solar coronal mass ejections (CMEs). Methods. We use muon data at cutoff rigidities ranging from 14 to 24 GV from the GRAPES-3 tracking muon telescope to identify FD events. We select those FD events that have a reasonably clean profile, and magnitude > 0.25%. We use IMF data from ACE/WIND spacecrafts. We look for correlations between the FD profile and that of the one hour averaged IMF. We ask if the diffusion of high energy protons into the large scale magnetic field is the cause of the lag observed between the FD and the IMF. Results. The enhancement of the IMF associated with FDs occurs mainly in the shock-sheath region, and the turbulence level in the magnetic field is also enhanced in this region. The observed FD profiles look remarkably similar to the IMF enhancement profiles. The FDs typically lag the IMF enhancement by a few hours. The lag corresponds to the time taken by high energy protons to diffuse into the magnetic field enhancement via cross-field diffusion. Conclusions. Our findings show that high rigidity FDs associated with CMEs are caused primarily by the cumulative diffusion of protons across the magnetic field enhancement in the turbulent sheath region between the shock and the CME.

We present a measurement of the $t\overline{t}$ production cross section in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ by the D0 experiment at the Fermilab Tevatron. The measurement is based on data from an integrated luminosity of approximately $125{\mathrm{pb}}^{\ensuremath{-}1}$ accumulated during the 1992--1996 collider run. We observe 39 $t\overline{t}$ candidate events in the dilepton and $\mathrm{lepton}+\mathrm{jets}$ decay channels with an expected background of $13.7\ifmmode\pm\else\textpm\fi{}2.2$ events. For a top quark mass of $173.3\mathrm{GeV}{/c}^{2}$, we measure the $t\overline{t}$ production cross section to be $5.5\ifmmode\pm\else\textpm\fi{}1.8\mathrm{pb}$.

Bottom-quark production in $\overline{p}p$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ is studied with $5{\mathrm{pb}}^{\ensuremath{-}1}$ of data collected in 1995 by the D0 detector at the Fermilab Tevatron Collider. The differential production cross section for $b$ jets in the central rapidity region ( $|{y}^{b}|&lt;1$) as a function of jet transverse energy is extracted from a muon-tagged jet sample. Within experimental and theoretical uncertainties, D0 results are found to be higher than, but compatible with, next-to-leading-order QCD predictions.

We report a search for effects of large extra spatial dimensions in pp collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions.

Results are presented from analyses of jet data produced in pp ¯collisions at ͱsϭ630 and 1800 GeV collected with the DØ detector during the 1994 -1995 Fermilab Tevatron Collider run.We discuss the details of detector calibration, and jet selection criteria in measurements of various jet production cross sections at ͱsϭ630 and 1800 GeV.The inclusive jet cross sections, the dijet mass spectrum, the dijet angular distribu- tions, and the ratio of inclusive jet cross sections at ͱsϭ630 and 1800 GeV are compared to next-to-leading- order QCD predictions.The order ␣ s 3 calculations are in good agreement with the data.We also use the data at ͱsϭ1800 GeV to rule out models of quark compositeness with a contact interaction scale less than 2.2 TeV at the 95% confidence level.

We report on measurements on inclusive cross sections times branching fractions into electrons for W and Z bosons produced in pp¯ collisions at s=1.8TeV. From an integrated luminosity of 84.5 pb−1 recorded in 1994–1995 using the DØ detector at the Fermilab Tevatron, we determine σ(pp¯→W+X)×B(W→eν)=2310±10(stat)±50(syst)±100(lum)pb and σ(pp¯→Z+X)×B(Z→ee)=221±3(stat)±4(syst)±10(lum)pb. From these, we derive σ(pp¯→W+X)×B(W→eν)/σ(pp¯→Z+X)×B(Z→ee)=10.43±0.15(stat)±0.20(syst)±0.10(NLO), B(W→eν)=0.1044±0.0015(stat)±0.0020(syst)±0.0017(theory)±0.0010(NLO), and ΓW=2.169±0.031(stat)±0.042(syst)±0.041(theory)±0.022(NLO)GeV. We use the latter to set a 95% confidence level upper limit on the partial decay width of the W boson into nonstandard model final states, ΓWinv, of 0.213 GeV. Combining these results with those from the 1992–1993 data gives σ(pp¯→W+X)×B(W→eν)/σ(pp¯→Z+X)×B(Z→ee)=10.51±0.25, ΓW=2.152±0.066GeV, and a 95% C.L. upper limit on ΓWinv of 0.191 GeV. Using a sample with a luminosity of 505 nb−1 taken at s=630GeV, we measure σ(pp¯→W+X)×B(W→eν)=658±67pb. Received 15 June 1999DOI:https://doi.org/10.1103/PhysRevD.61.072001©2000 American Physical Society

The inclusive cross sections times leptonic branching ratios for W and Z boson production in PbarP collisions at Sqrt(s)=1.8 TeV were measured using the D0 detector at the Fermilab Tevatron collider: Sigma_W*B(W->e, nu) = 2.36 +/- 0.07 +/- 0.13 nb, Sigma_W*B(W->mu,nu) = 2.09 +/- 0.23 +/- 0.11 nb, Sigma_Z*B(Z-> e, e) = 0.218 +/- 0.011 +/- 0.012 nb, Sigma_Z*B(Z->mu,mu) = 0.178 +/- 0.030 +/- 0.009 nb. The first error is the combined statistical and systematic uncertainty, and the second reflects the uncertainty in the luminosity. For the combined electron and muon analyses we find: [Sigma_W*B(W->l,nu)]/[Sigma_Z*B(Z->l,l)] = 10.90 +/- 0.49. Assuming Standard Model couplings, this result is used to determine the width of the W boson: Gamma(W) = 2.044 +/- 0.093 GeV.

We present a measurement of the Drell-Yan cross section at high dielectron invariant mass using $120\mathrm{pb}{}^{\ensuremath{-}1}$ of data collected in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ by the D0 Collaboration during 1992--1996. No deviation from standard model expectations is observed. We use the data to set limits on the quark-electron compositeness scale. The $95%$ confidence level lower limits on the compositeness scale vary between 3.3 and 6.1 TeV depending on the assumed form of the effective contact interaction.

The DØ detector is used to study pp̄ collisions at the 1800 and 630 GeV center-of-mass energies available at the Fermilab Tevatron. To measure jets, the detector uses a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. Understanding the jet energy calibration is not only crucial for precision tests of QCD, but also for the measurement of particle masses and the determination of physics backgrounds associated with new phenomena. This paper describes the energy calibration of jets observed with the DØ detector at the two pp̄ center-of-mass energies in the transverse energy and pseudorapidity range ET>8 GeV and |η|<3.

Using the D0 detector at the 1.8 TeV $\overline{p}p$ Fermilab Tevatron collider, we have measured the inclusive dijet mass spectrum in the central pseudorapidity region $|{\ensuremath{\eta}}_{\mathrm{jet}}|&lt;1.0$ for dijet masses greater than $200\mathrm{GeV}{/c}^{2}$. We have also measured the ratio of spectra $\ensuremath{\sigma}(|{\ensuremath{\eta}}_{\mathrm{jet}}|&lt;0.5)/\ensuremath{\sigma}(0.5&lt;|{\ensuremath{\eta}}_{\mathrm{jet}}|&lt;1.0)$. The order ${\ensuremath{\alpha}}_{s}^{3}$ quantum chromodynamics predictions are in good agreement with the data and we rule out models of quark compositeness with a contact interaction scale $&lt;2.4\mathrm{TeV}$ at the $95%$ confidence level.

We have made a precise measurement of the central inclusive jet cross section at sqrt(s) = 1.8 TeV. The measurement is based on an integrated luminosity of 92 pb-1 collected at the Fermilab Tevatron pbar-p Collider with the D-Zero detector. The cross section, reported as a function of jet transverse energy (ET >= 60 GeV) in the pseudorapidity interval |eta| <= 0.5, is in good agreement with predictions from next-to-leading order quantum chromodynamics.

We examine properties of tt¯ candidate events in lepton + jets final states to establish the helicities of W bosons in t→W+b decays. Our analysis is based on a direct calculation of a probability density for each event to correspond to a tt¯ final state, as a function of the helicity of the W boson. Using the 125 events/pb of data collected by the DØ experiment at the Fermilab Tevatron pp¯ Collider at s=1.8TeV, we obtain a longitudinal helicity fraction F0=0.56±0.31, consistent with the prediction of F0=0.70 from the standard model.

We present the results of a search for the production of new particles decaying into two jets in $\overline{p}p$ collisions at $\sqrt{s}=1.8\mathrm{TeV},$ using the D\O{} 1992--1995 data set corresponding to ${109\mathrm{}\mathrm{pb}}^{\ensuremath{-}1}.$ We exclude at the 95% confidence level the production of excited quarks ${(q}^{*})$ with masses below 775 GeV/${c}^{2},$ the most restrictive limit to date. We also exclude standard-model-like ${W}^{\ensuremath{'}}$ ${(Z}^{\ensuremath{'}})$ bosons with masses between 300 and 800 GeV/${c}^{2}$ (400 and 640 GeV/${c}^{2}).$ A ${W}^{\ensuremath{'}}$ boson with mass $&lt;786\mathrm{GeV}{/c}^{2}$ has been excluded by previous measurements, and our lower limit is therefore the most stringent to date.

We present a search for large extra dimensions (ED) in pp collisions at a center-of-mass energy of 1.8 TeV using data collected by the DØ detector at the Fermilab Tevatron in 1994-1996. Data corresponding to 78.8+/-3.9 pb(-1) are examined for events with large missing transverse energy, one high-p(T) jet, and no isolated muons. There is no excess observed beyond expectation from the standard model, and we place lower limits on the fundamental Planck scale of 1.0 and 0.6 TeV for 2 and 7 ED, respectively.

<i>Aims. <i/>We seek to estimate the average level of MHD turbulence near coronal mass ejection (CME) fronts as they propagate from the Sun to the Earth.<i>Methods. <i/>We examined the cosmic ray data from the GRAPES-3 tracking muon telescope at Ooty, together with the data from other sources for three closely observed Forbush decrease events. Each of these event is associated with frontside halo coronal mass ejections (CMEs) and near-Earth magnetic clouds. The associated Forbush decreases are therefore expected to have significant contributions from the cosmic-ray depressions inside the CMEs/ejecta. In each case, we estimate the magnitude of the Forbush decrease using a simple model for the diffusion of high-energy protons through the largely closed field lines enclosing the CME as it expands and propagates from the Sun to the Earth. The diffusion of high-energy protons is inhibited by the smooth, large-scale magnetic field enclosing the CME and aided by the turbulent fluctuations near the CME front. We use estimates of the cross-field diffusion coefficient derived from the published results of extensive Monte Carlo simulations of cosmic rays propagating through turbulent magnetic fields. We then compare our estimates with the magnitudes of the observed Forbush decreases.<i>Results. <i/>Our method helps constrain the ratio of energy density in the turbulent magnetic fields to that in the mean magnetic fields near the CME fronts. This ratio is found to be ~2% for the 2001 April 11 Forbush decrease event, ~6% for the 2003 November 20 Forbush decrease event and ~249% for the much more energetic event of 2003 October 29.

Extensive measurements have been made with pions, electrons and muons on four production wedges of the compact muon solenoid (CMS) hadron barrel (HB) calorimeter in the H2 beam line at CERN with particle momenta varying from 20 to 300 GeV/c. The time structure of the events was measured with the full chain of preproduction front-end electronics running at 34 MHz. Moving-wire radioactive source data were also collected for all scintillator layers in the HB. The energy dependent time slewing effect was measured and tuned for optimal performance.

The GRAPES-3 tracking muon telescope in Ooty, India measures muon intensity at high cutoff rigidities (15–24 GV) along nine independent directions covering 2.3 sr. The arrival of a coronal mass ejection on 22 June 2015 18:40 UT had triggered a severe G4-class geomagnetic storm (storm). Starting 19:00 UT, the GRAPES-3 muon telescope recorded a 2 h high-energy (∼20 GeV) burst of galactic cosmic rays (GCRs) that was strongly correlated with a 40 nT surge in the interplanetary magnetic field (IMF). Simulations have shown that a large (17×) compression of the IMF to 680 nT, followed by reconnection with the geomagnetic field (GMF) leading to lower cutoff rigidities could generate this burst. Here, 680 nT represents a short-term change in GMF around Earth, averaged over 7 times its volume. The GCRs, due to lowering of cutoff rigidities, were deflected from Earth’s day side by ∼210° in longitude, offering a natural explanation of its night-time detection by the GRAPES-3. The simultaneous occurrence of the burst in all nine directions suggests its origin close to Earth. It also indicates a transient weakening of Earth’s magnetic shield, and may hold clues for a better understanding of future superstorms that could cripple modern technological infrastructure on Earth, and endanger the lives of the astronauts in space.Received 16 June 2016DOI:https://doi.org/10.1103/PhysRevLett.117.171101© 2016 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCosmic ray & astroparticle detectorsCosmic ray propagationParticle astrophysicsPhysical SystemsCoronal mass ejectionsGravitation, Cosmology & Astrophysics

Using data corresponding to an integrated luminosity of $79{\mathrm{pb}}^{\ensuremath{-}1}$, D0 has searched for events containing multiple jets and large missing transverse energy in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\phantom{\rule{0ex}{0ex}}\mathrm{TeV}$ at the Fermilab Tevatron collider. Observing no significant excess beyond what is expected from the standard model, we set limits on the masses of squarks and gluinos and on the model parameters ${m}_{0}$ and ${m}_{1/2}$, in the framework of the minimal low-energy supergravity models of supersymmetry. For $\mathrm{tan}\ensuremath{\beta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ and ${A}_{0}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$, with $\ensuremath{\mu}&lt;0$, we exclude all models with ${m}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{q}}&lt;250\phantom{\rule{0ex}{0ex}}\mathrm{GeV}{/c}^{2}$. For models with equal squark and gluino masses, we exclude $m&lt;260\phantom{\rule{0ex}{0ex}}\mathrm{GeV}{/c}^{2}$.

We present a measurement of the differential cross section as a function of transverse momentum of the Z boson in ppbar collisions at sqrt{s}=1.8 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider during 1994--1996. We find good agreement between our data and the NNLO resummation prediction and extract values of the non-perturbative parameters for the resummed prediction from a fit to the differential cross section.

We present results on dijet production via hard color-singlet exchange in proton-antiproton collisions at s=630 GeV and 1800 GeV using the DØ detector. The fraction of dijet events produced via color-singlet exchange is measured as a function of jet transverse energy, separation in pseudorapidity between the two highest transverse energy jets, and proton-antiproton center-of-mass energy. The results are consistent with a color-singlet fraction that increases with an increasing fraction of quark-initiated processes and inconsistent with two-gluon models for the hard color-singlet.

We present a quasi-model-independent search for the physics responsible for electroweak symmetry breaking.We define final states to be studied, and construct a rule that identifies a set of relevant variables for any particular final state.A new algorithm ͑''SLEUTH''͒ searches for regions of excess in those variables and quantifies the significance of any detected excess.After demonstrating the sensitivity of the method, we apply it to the semi-inclusive channel eX collected in 108 pb Ϫ1 of pp ¯collisions at ͱsϭ1.8 TeV at the DO " experiment during 1992-1996 at the Fermilab Tevatron.We find no evidence of new high p T physics in this sample.

A measurement of the mass of the W boson is presented based on a sample of 5982 W→eν decays observed in p¯p collisions at √s=1.8TeV with the D0 detector during the 1992–1993 run. From a fit to the transverse mass spectrum, combined with measurements of the Z boson mass, the W boson mass is measured to be MW=80.350±0.140(stat)±0.165(syst)±0.160(scale)GeV/c2.Received 11 July 1996DOI:https://doi.org/10.1103/PhysRevLett.77.3309©1996 American Physical Society

The composition and energy spectrum of primary cosmic rays (PCRs) are the only observables at high energies to study the nature of sources accelerating PCRs to �1000 TeV. These observables have been directly measured up to ∼300 TeV with detectors aboard balloons and satellites. But measurements at >1000 TeV have to be obtained indirectly from ground-based observations of extensive air showers. However, their interpretation relies on an inadequate knowledge of hadronic interactions at �1000 TeV. The GRAPES-3 experiment is designed to operate at �30 TeV providing a sizable overlap in energy with direct measurements, enabling the selection of a suitable model of hadronic interactions at ∼1000 TeV. We present salient features of GRAPES-3 including details of muon multiplicity distributions observed with a 560 m 2 detector as a function of shower size from an analysis of data of 545 days. These distributions were compared with expectations from Monte Carlo simulations, using some of the hadronic interaction generators in CORSIKA, to deduce energy spectra of five nuclear groups in the 100–1000 TeV region. A comparison of GRAPES-3 results with direct measurements indicates that SIBYLL provides a good description of hadronic interactions for interpreting our data. These measurements extend energy spectra and composition of PCRs that is consistent with extrapolation of direct measurements. (Some figures may appear in colour only in the online journal)

Abstract As part of its HL-LHC upgrade program, the CMS collaboration is developing a High Granularity Calorimeter (CE) to replace the existing endcap calorimeters. The CE is a sampling calorimeter with unprecedented transverse and longitudinal readout for both electromagnetic (CE-E) and hadronic (CE-H) compartments. The calorimeter will be built with ∼30,000 hexagonal silicon modules. Prototype modules have been constructed with 6-inch hexagonal silicon sensors with cell areas of 1.1 cm 2 , and the SKIROC2-CMS readout ASIC. Beam tests of different sampling configurations were conducted with the prototype modules at DESY and CERN in 2017 and 2018. This paper describes the construction and commissioning of the CE calorimeter prototype, the silicon modules used in the construction, their basic performance, and the methods used for their calibration.

We have searched for the pair production of first generation scalar leptoquarks in the eejj channel using the full data set (123pb−1) collected with the D0 detector at the Fermilab Tevatron during 1992–1996. We observe no candidates with an expected background of approximately 0.4 events. Comparing the experimental 95% confidence level upper limit to theoretical calculations of the cross section with the assumption of a 100% branching fraction of eq, we set a lower limit on the mass of a first generation scalar leptoquark of 225GeV/c2. The results of this analysis rule out the interpretation of the excess of high Q2 events at DESY HERA as leptoquarks which decay exclusively to eq.Received 21 July 1997DOI:https://doi.org/10.1103/PhysRevLett.79.4321©1997 American Physical Society

We have measured the W W gauge boson coupling parameters using p p ! ` + X (`= e; ) events at p s = 1:8 TeV.The data, corresponding to an integrated luminosity of 89:1 pb 1 , were collected using the D detector at the Fermilab Tevatron Collider.The measured cross section times branching ratio for p p ! W + X with p T > 10 GeV/c and R ` > 0:7 is 11:8 +1:7 1:6 2:0 pb, in agreement with the Standard Model prediction.The one degree of freedom 95% con dence level limits on individual CP-conserving parameters are 0:98 < < 1:01 and 0:33 < < 0:31.Similar limits are set on the CP-violating coupling parameters.

We have searched for first generation scalar leptoquark (LQ) pairs in the $e\ensuremath{\nu}+\mathrm{jets}$ channel using $p\overline{p}$ collider data $(\ensuremath{\int}L\mathrm{dt}\ensuremath{\approx}115{\mathrm{pb}}^{\ensuremath{-}1})$ collected by the D0 experiment at the Fermilab Tevatron during 1992--1996. The analysis yields no candidate events. We combine the results with those from the $ee+\mathrm{jets}$ and $\ensuremath{\nu}\ensuremath{\nu}+\mathrm{jets}$ channels to obtain 95% confidence level (C.L.) upper limits on the LQ pair production cross section as a function of mass and of $\ensuremath{\beta}$, the branching fraction to a charged lepton. Comparing with the next-to-leading order theory, we set 95% C.L. lower limits on the LQ mass of 225, 204, and $79\mathrm{GeV}{/c}^{2}$ for $\ensuremath{\beta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$, $\frac{1}{2}$, and 0, respectively.

A measurement of the cross section for production of single, isolated photons is reported for transverse energies in the range of 10--125 GeV for two regions of pseudorapidity, $|\ensuremath{\eta}|&lt;0.9$ and $1.6&lt;|\ensuremath{\eta}|&lt;2.5$. The data represent $12.9{\mathrm{pb}}^{\ensuremath{-}1}$ of integrated luminosity accumulated in $\overline{p}p$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ and recorded with the D0 detector at the Fermilab Tevatron Collider. The background, predominantly from jets which fragment to neutral mesons, is estimated using the longitudinal shower shape in the calorimeter. In both pseudorapidity regions the cross section is found to agree with the next-to-leading order QCD prediction for $30\ensuremath{\lesssim}{E}_{T}^{\ensuremath{\gamma}}\ensuremath{\lesssim}80\mathrm{GeV}$.

We present a search for charged Higgs bosons in decays of pair-produced top quarks in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( ${M}_{{H}^{\ifmmode\pm\else\textpm\fi{}}},\mathrm{tan}\ensuremath{\beta}$) parameter space where the decay $t\ensuremath{\rightarrow}{\mathrm{H}}^{+}b$ has a branching fraction $&gt;0.36$ and $B({H}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}\ensuremath{\tau}{\ensuremath{\nu}}_{\ensuremath{\tau}})$ is large.

The distribution of the transverse energy in jets has been measured in pp collisions at s=1.8 TeV TeV using the DØ detector at Fermilab. This measurement of the jet shape is made as a function of jet transverse energy in both the central and forward rapidity regions. Jets are shown to narrow both with increasing transverse energy and with increasing rapidity. Next-to-leading order partonic QCD calculations are compared to the data. Although the calculations qualitatively describe the data, they are shown to be very dependent on renormalization scale, parton clustering algorithm, and jet direction definition and they fail to describe the data in all regions consistently.

The GRAPES-3 extensive air shower (EAS) array started operation with 256 scintillator detectors at Ooty in India. Each detector is viewed by a fast photomultiplier tube (PMT) mounted at a height of 60 cm above the scintillator. However, for further expansion of the array, an alternative readout of the scintillator using wave-length shifting (WLS) fibers is employed. This resulted in improved performance with a larger photon signal and a more uniform response. With the inclusion of a second PMT, the dynamic range for particle detection has been increased to ∼5 × 103 particles m−2. We now use plastic scintillators, developed in-house to cut costs. The measurement of the density spectrum, shows a power law dependence with an index γ = 1.57 ± 0.04. Using the zenith angle dependence of the density spectrum, an attenuation length Λa = 98–106 g cm−2 for the EAS is obtained. These measurements are found to be consistent with the results reported earlier by other groups.

We have searched for central production of a pair of photons with high transverse energies in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ using $70{\mathrm{pb}}^{\ensuremath{-}1}$ of data collected with the D0 detector at the Fermilab Tevatron in 1994--1996. If they exist, virtual heavy pointlike Dirac monopoles could rescatter pairs of nearly real photons into this final state via a box diagram. We observe no excess of events above background, and set lower $95%$ C.L. limits of 610, 870, or $1580\mathrm{GeV}{/c}^{2}$ on the mass of a spin 0, $1/2$, or 1 Dirac monopole.

A study of the particle multiplicity between jets with large rapidity separation has been performed using the D0 detector at the Fermilab Tevatron p¯p Collider operating at √s=1.8TeV. A significant excess of low-multiplicity events is observed above the expectation for color-exchange processes. The measured fractional excess is 1.07±0.10(stat)+0.25−0.13(syst)%, which is consistent with a strongly interacting color-singlet (colorless) exchange process and cannot be explained by electroweak exchange alone. A lower limit of 0.80% (95% C.L.) is obtained on the fraction of dijet events with color-singlet exchange, independent of the rapidity gap survival probability.Received 20 September 1995DOI:https://doi.org/10.1103/PhysRevLett.76.734©1996 American Physical Society

The D0 collaboration has performed a study of spin correlation in $t\overline{t}$ production for the process $t\overline{t}\ensuremath{\rightarrow}{\mathrm{bW}}^{+}\overline{b}{W}^{\ensuremath{-}}$, where the $W$ bosons decay to $e\ensuremath{\nu}$ or $\ensuremath{\mu}\ensuremath{\nu}$. A sample of six events was collected during an exposure of the D0 detector to an integrated luminosity of approximately $125{\mathrm{pb}}^{\ensuremath{-}1}$ of $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ $p\overline{p}$ collisions. The standard model (SM) predicts that the short lifetime of the top quark ensures the transmission of any spin information at production to the $t\overline{t}$ decay products. The degree of spin correlation is characterized by a correlation coefficient $\ensuremath{\kappa}$. We find that $\ensuremath{\kappa}&gt;\ensuremath{-}0.25$ at the $68%$ confidence level, in agreement with the SM prediction of $\ensuremath{\kappa}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.88$.

We have measured the dijet angular distribution in $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\phantom{\rule{0ex}{0ex}}\mathrm{TeV}p\overline{p}$ collisions using the D0 detector. Order ${\ensuremath{\alpha}}_{s}^{3}$ QCD predictions are in good agreement with the data. At 95% confidence limit the data exclude models of quark compositeness in which the contact interaction scale is below 2 TeV.

The results of a search for W boson pair production in pp¯ collisions at s=1.8TeV with subsequent decay to dilepton ( eμ,ee, and μμ) channels are presented. One event is observed with an expected background of 0.56±0.13 events with an integrated luminosity of approximately 14pb−1. Assuming equal strengths for the WWZ and WWγ gauge boson coupling parameters κ and λ, limits on the CP-conserving anomalous coupling constants are −2.6<Δκ<2.8 and −2.1<λ<2.1 at the 95% confidence level.Received 10 March 1995DOI:https://doi.org/10.1103/PhysRevLett.75.1023©1995 American Physical Society

This paper presents the first measurement of inclusive J͞c production cross section in the forward pseudorapidity region 2.5 # jh J͞c j # 3.7 in pp collisions at p s 1.8 TeV.The results are based on 9.8 pb 21 of data collected using the D0 detector at the Fermilab Tevatron Collider.The inclusive J͞c cross section for transverse momenta between 1 and 16 GeV͞c is compared with theoretical models of charmonium production.[S0031-9007(98)08183-6

We have measured the $\mathrm{ZZ}\ensuremath{\gamma}$ and $Z\ensuremath{\gamma}\ensuremath{\gamma}$ couplings by studying $13.1{\mathrm{pb}}^{\ensuremath{-}1}$ of $p\overline{p}\ensuremath{\rightarrow}{E}_{t}\ensuremath{\gamma}+X$ data at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ with the D\O{} detector at the Fermilab Tevatron Collider. This is the first study of hadronic $Z\ensuremath{\gamma}$ production in the neutrino decay channel. Combining this measurement with our previous results using $Z\ensuremath{\rightarrow}\mathrm{ee}$ and $\ensuremath{\mu}\ensuremath{\mu}$ yields the most stringent 95% C.L. limits to date on anomalous couplings: $|{h}_{30}^{Z}|&lt;0.4$, $|{h}_{40}^{Z}|&lt;0.06$ ( $\ensuremath{\Lambda}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}750\mathrm{GeV}$).

This Letter describes a measurement of the muon cross section originating from $b$-quark decay in the forward rapidity range $2.4&lt;|{y}^{\ensuremath{\mu}}|&lt;3.2$ in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$. The data used in this analysis were collected by the D0 experiment at the Fermilab Tevatron. We find that next-to-leading-order QCD calculations underestimate $b$-quark production by a factor of 4 in the forward rapidity region.

We apply a quasi-model-independent strategy ("Sleuth") to search for new high p_T physics in approximately 100 pb^-1 of ppbar collisions at sqrt(s) = 1.8 TeV collected by the DZero experiment during 1992-1996 at the Fermilab Tevatron. Over thirty-two e mu X, W+jets-like, Z+jets-like, and 3(lepton/photon)X exclusive final states are systematically analyzed for hints of physics beyond the standard model. Simultaneous sensitivity to a variety of models predicting new phenomena at the electroweak scale is demonstrated by testing the method on a particular signature in each set of final states. No evidence of new high p_T physics is observed in the course of this search, and we find that 89% of an ensemble of hypothetical similar experimental runs would have produced a final state with a candidate signal more interesting than the most interesting observed in these data.

We apply a quasi-model-independent strategy ("Sleuth") to search for new high p(T) physics in approximately 100 pb(-1) of pp collisions at square root of (s) = 1.8 TeV collected by the D0 experiment during 1992-1996 at the Fermilab Tevatron. We systematically analyze many exclusive final states and demonstrate sensitivity to a variety of models predicting new phenomena at the electroweak scale. No evidence of new high p(T) physics is observed.

We present a search for electroweak production of single top quarks in the electronϩjets and muonϩjets decay channels.The measurements use Ϸ90 pb Ϫ1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DO " detector between 1992 and 1995.We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process pp ¯→tbϩX of 39 pb.The upper limit for the t-channel process pp ¯→tqbϩX is 58 pb.

The GRAPES-3 large area (560 m2) tracking muon telescope is operating at Ooty in India since 2001. It records 4 × 109 muons of energy ≥ 1 GeV every day. These high statistics data have enabled extremely sensitive measurements of solar phenomena, including the solar anisotropies, Forbush decreases, coronal mass ejections etc. to be made. However, prior to such studies, the variation in observed muon rate caused by changes in atmospheric pressure needs to be corrected. Traditionally, the pressure coefficient (β) for the muon rate was derived from the observed data. But the influence of various solar effects makes the measurement of β somewhat difficult. In the present work, a different approach to circumvent this difficulty was used to measure β, almost independent of the solar activity. This approach exploits a small amplitude (∼1 hPa) periodic (12 h) variation of atmospheric pressure at Ooty that introduces a synchronous variation in the muon rate. By using the fast Fourier transform technique the spectral power distributions at 12 h from the atmospheric pressure, and muon rate were used to measure β. The value of pressure coefficient was found to be β=(−0.128±0.005)% hPa−1.

Abstract The Compact Muon Solenoid collaboration is designing a new high-granularity endcap calorimeter, HGCAL, to be installed later this decade. As part of this development work, a prototype system was built, with an electromagnetic section consisting of 14 double-sided structures, providing 28 sampling layers. Each sampling layer has an hexagonal module, where a multipad large-area silicon sensor is glued between an electronics circuit board and a metal baseplate. The sensor pads of approximately 1.1 cm 2 are wire-bonded to the circuit board and are readout by custom integrated circuits. The prototype was extensively tested with beams at CERN's Super Proton Synchrotron in 2018. Based on the data collected with beams of positrons, with energies ranging from 20 to 300 GeV, measurements of the energy resolution and linearity, the position and angular resolutions, and the shower shapes are presented and compared to a detailed Geant4 simulation.

HCPV cells are known for their high efficiency in converting sunlight into electricity. However, this increased efficiency also generates higher levels of heat, posing a risk of cell damage. Therefore, the study proposes the combination of a phase change material (CPCM) and liquid flow in hybrid wavy microchannels to ensure stable temperature within the high-concentration photovoltaic (HCPV) cells. A three-dimensional numerical model has been developed to capture the thermal behavior of PCM integrated with water cooling in a microchannel heat sink. The comparison and analysis involved contrasting cases with phase change material (PCM) and cases without PCM. The PCM cases were studied at Reynolds number (Re) 100, while the cases without PCM were investigated at Reynolds numbers of 100 and 200. Three distinct types of PCM were employed, specifically OM 32, Rt 35, and PA - SA/EG. The various microchannel geometries under consideration included Raccoon, wavy, and hybrid wavy microchannels. The results showed that using both PCM and water cooling in a microchannel is preferable over using only water cooling. The outcomes reveal that employing PCM 3 (CPCM) in conjunction with the raccoon wavy microchannel design, there is an 11.61% reduction in the maximum pressure drop, along with a decrease of 6.58% in the maximum solid substrate temperature. Moreover, this configuration attains the highest electrical efficiency, reaching 39.32%.

Abstract GRAPES-3 is a mid-altitude (2200 m) and near-equatorial (11.°4N) air shower array, overlapping in its field of view for cosmic-ray observations with experiments that are located in the Northern and Southern Hemispheres. We analyze a sample of 3.7 × 10 9 cosmic-ray events collected by the GRAPES-3 experiment between 2013 January 1 and 2016 December 31 with a median energy of ∼16 TeV for study of small-scale (&lt;60°) angular-scale anisotropies. We observed two structures, labeled A and B, that deviate from the expected isotropic distribution of cosmic rays in a statistically significant manner. Structure A spans 50°–80° in R.A. and from −15° to 30° in decl. The relative excess observed in structure A is at the level of (6.5 ± 1.3) × 10 −4 with a statistical significance of 6.8 standard deviations. Structure B is observed in the R.A. range 110°–140° and at decl. from −10° to 30°. The relative excess observed in this region is at the level of (4.9 ± 1.4) × 10 −4 with a statistical significance of 4.7 standard deviations. These structures are consistent with those reported by Milagro, ARGO-YBJ, and HAWC. These observations could provide a better understanding of the sources of cosmic rays, their propagation, and the magnetic structures in our Galaxy.

Abstract The GRAPES-3 extensive air shower (EAS) array has been designed to study cosmic rays from 10 $$^{13}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow /> <mml:mn>13</mml:mn> </mml:msup> </mml:math> –10 $$^{16}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow /> <mml:mn>16</mml:mn> </mml:msup> </mml:math> eV. It employs 400 scintillator detectors spread across 25,000 m $$^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow /> <mml:mn>2</mml:mn> </mml:msup> </mml:math> , mainly of cone-type and fiber-type, each covering a 1 m $$^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow /> <mml:mn>2</mml:mn> </mml:msup> </mml:math> area. These detectors record EAS particle densities and arrival times, which are crucial for determining primary particle energy and direction. A decade (2013–2022) of EAS data is analyzed to investigate the dependence of particle densities on ambient temperature and atmospheric pressure. Notably, ambient temperature exhibits a delayed response, with a more pronounced delay in fiber-type detectors, while cone-type detectors exhibit a higher observed temperature coefficient. In contrast, atmospheric pressure instantly and uniformly affects both detector types, with Monte Carlo simulations backing the observed pressure coefficient. These findings established a reliable pressure coefficient for EAS within this distinctive energy range and contributed to the refinement of correction algorithms, ultimately improving particle density precision for more accurate shower parameter estimates.

The GRAPES-3 tracking muon telescope located at Ooty (India) records short-term variations in the muon intensity during major thunderstorms, termed thunderstorm-induced muon events (TIMEs). Its excellent angular resolution, coupled with high statistics, allows us to observe subtle directional variations in muon rate. We detected 169 statistically significant events during the five-year period from 2006 through 2010. The monthly and seasonal variation patterns of the observed TIMEs were discussed, emphasizing their occurrence and climatological aspects. The annual diurnal pattern was plotted with the Carnegie curve, considering their possible causal link with the global electric circuit. The work represents the first report from any experiment for such an extended period in an uninterrupted manner.

We search for inclusive high ${E}_{T}$ diphoton events with large missing transverse energy in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\phantom{\rule{0ex}{0ex}}\mathrm{TeV}$. Such events are expected from pair production of charginos and neutralinos within the framework of the minimal supersymmetric standard model with a light gravitino. No excess of events is observed. In that model, and assuming gaugino mass unification at the GUT scale, we obtain a 95% C.L. exclusion region in the supersymmetry parameter space and lower mass bounds of $150\mathrm{GeV}{/c}^{2}$ for the lightest chargino and $77\mathrm{GeV}{/c}^{2}$ for the lightest neutralino.

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The W W γ gauge boson couplings were measured using pp → ℓνγ + X (ℓ = e, µ) events at √ s = 1.8 TeV observed with the DØ detector at the Fermilab Tevatron Collider.The signal, obtained from the data corresponding to an integrated luminosity of 13.8 pb -1 , agrees well with the Standard Model prediction.A fit to the photon transverse energy spectrum yields limits at the 95% confidence level on the CP-conserving anomalous coupling parameters of -1.6 < ∆κ < 1.8 (λ = 0) and -0.6 < λ < 0.6 (∆κ = 0).

We present a measurement of the W boson mass using data collected by the DØ experiment at the Fermilab Tevatron during 1994–1995. We identify W bosons by their decays to eν final states where the electron is detected in a forward calorimeter. We extract the W boson mass MW by fitting the transverse mass and transverse electron and neutrino momentum spectra from a sample of 11 089 −→Weν decay candidates. We use a sample of 1687 dielectron events, mostly due to →Zee decays, to constrain our model of the detector response. Using the forward calorimeter data, we measure MW=80.691±0.227GeV. Combining the forward calorimeter measurements with our previously published central calorimeter results, we obtain MW=80.482±0.091GeV. Received 23 August 1999DOI:https://doi.org/10.1103/PhysRevD.62.092006©2000 American Physical Society

The large area (560 m2) GRAPES-3 tracking muon telescope has been operating uninterruptedly at Ooty, India since 2001. Every day, it records 4 × 109 muons of ≥ 1 GeV with an angular resolution of ∼ 4°. The variation of atmospheric temperature affects the rate of decay of muons produced by the galactic cosmic rays (GCRs), which in turn modulates the muon intensity. By analyzing the GRAPES-3 data of six years (2005–2010), a small (amplitude ∼ 0.2%) seasonal variation (1 year (Yr) period) in the intensity of muons could be measured. The effective temperature 'Teff' of the upper atmosphere also displays a periodic variation with an amplitude of ∼ 1 K which was responsible for the observed seasonal variation in the muon intensity. At GeV energies, the muons detected by the GRAPES-3 are expected to be anti-correlated with Teff. The anti-correlation between the seasonal variation of Teff, and the muon intensity was used to measure the temperature coefficient αT by fast Fourier transform (FFT) technique. The magnitude of αT was found to scale with the assumed attenuation length 'λ' of the hadrons in the range λ = 80–180 g cm−2. However, the magnitude of the correction in the muon intensity was found to be almost independent of the value of λ used. For λ = 120 g cm−2 the value of temperature coefficient αT was found to be (−0.17±0.02)% K−1.

We present a measurement of t t production in pp collisions at √ s = 1.8 TeV from 110 pb -1 of data collected in the all-jets decay channel with the DØ detector at Fermilab.A neural network analysis yields a cross section of 7.1 ± 2.8 (stat.)± 1.5 (syst.)pb, at a top quark mass (mt) of 172.1 GeV/c 2 .Using previous DØ measurements from dilepton and single lepton channels, the combined DØ result for the t t production cross section is 5.9 ± 1.2 (stat.)± 1.1 (syst.)pb for mt = 172.1 GeV/c 2 .

We report a measurement of the W boson mass based on an integrated luminosity of 82pb−1 from p¯p collisions at √s=1.8TeV recorded in 1994–1995 by the D0 detector at the Fermilab Tevatron. We identify W bosons by their decays to eν and extract the mass by fitting the transverse mass spectrum from 28 323 W boson candidates. A sample of 3563 dielectron events, mostly due to Z→ee decays, constrains models of W boson production and the detector. We measure MW=80.44±0.10(stat)±0.07(syst)GeV. By combining this measurement with our result form the 1992–1993 data set, we obtain MW=80.43±0.11GeV.Received 23 December 1997DOI:https://doi.org/10.1103/PhysRevLett.80.3008©1998 American Physical Society

We present a study of Z +gamma + X production in p-bar p collisions at sqrt{S}=1.8 TeV from 97 (87) pb^{-1} of data collected in the eegamma (mumugamma) decay channel with the D0 detector at Fermilab. The event yield and kinematic characteristics are consistent with the Standard Model predictions. We obtain limits on anomalous ZZgamma and Zgammagamma couplings for form factor scales Lambda = 500 GeV and Lambda = 750 GeV. Combining this analysis with our previous results yields 95% CL limits |h{Z}_{30}| < 0.36, |h{Z}_{40}| < 0.05, |h{gamma}_{30}| < 0.37, and |h{gamma}_{40}| < 0.05 for a form factor scale Lambda=750 GeV.

We have studied t t ¯production using multijet final states in pp ¯collisions at a center-of-mass energy of 1.8 TeV, with an integrated luminosity of 110.3 pb Ϫ1 .Each of the top quarks with these final states decays exclusively to a bottom quark and a W boson, with the W bosons decaying into quark-antiquark pairs.The analysis has been optimized using neural networks to achieve the smallest expected fractional uncertainty on the t t ¯production cross section, and yields a cross section of 7.1Ϯ2.8͑stat͒Ϯ1.5͑syst͒ pb, assuming a top quark mass of 172.1 GeV/c 2 .Combining this result with previous DO " measurements, where one or both of the W bosons decay leptonically, gives a t t ¯production cross section of 5.9Ϯ1.2(stat)Ϯ1.1 (syst) pb.͓S0556-2821͑99͒03607-3͔

A search for new physics has been carried out in the channel p¯p→γγ+ET, as expected in various supersymmetric models. We require two photons with transverse energy EγT>12GeV and pseudorapidity |ηγ|<1.1. The distribution of missing transverse energy ( ET) is consistent with background and no events have ET>25GeV. We set limits on production cross sections for selectron, sneutrino, and neutralino pairs, decaying into photons, which range from about 400 fb to 1 pb depending on the sparticle masses. A general limit of 185 fb (95% C.L.) is set on σ(p¯p→γγET+X), where EγT>12GeV, |ηγ|<1.1, and ET>25GeV.Received 12 December 1996DOI:https://doi.org/10.1103/PhysRevLett.78.2070©1997 American Physical Society

Inclusive dijet production at large pseudorapidity intervals (Deltaeta) between the two jets has been suggested as a regime for observing Balitsky-Fadin-Kuraev-Lipatov (BFKL) dynamics. We have measured the dijet cross section for large Deltaeta in pp collisions at sqrt[s]=1800 and 630 GeV using the D0 detector. The partonic cross section increases strongly with the size of Deltaeta. The observed growth is even stronger than expected on the basis of BFKL resummation in the leading logarithmic approximation. The growth of the partonic cross section can be accommodated with an effective BFKL intercept of alphaBFKL(20 GeV)=1.65+/-0.07.

The shape of the transverse momentum distribution of W bosons ( pTW) produced in pp¯ collisions at s=1.8 TeV is measured with the D0 detector at Fermilab. The result is compared with QCD perturbative and resummation calculations over the pTW range from 0 to 200GeV/c. The shape of the distribution is consistent with the theoretical prediction.Received 3 March 1998DOI:https://doi.org/10.1103/PhysRevLett.80.5498©1998 American Physical Society

We performed a direct search for the anomalous ZZγ and Zγγ couplings by studying p¯p→ℓℓγ+X (ℓ=e,μ) events at √s=1.8 TeV with the D0 detector at the Fermilab Tevatron Collider. A fit to the transverse energy spectrum of the photon in the signal events, based on the data set corresponding to an integrated luminosity of 14.3pb−1 ( 13.7pb−1) for the electron (muon) channel, yields the following 95% confidence level limits on the anomalous CP-conserving ZZγ couplings: |hZ30|<1.8 ( hZ40=0) and |hZ40|<0.5 ( hZ30=0), for a form-factor scale Λ=500 GeV. Limits for the Zγγ couplings and CP-violating couplings are also discussed.Received 10 March 1995DOI:https://doi.org/10.1103/PhysRevLett.75.1028©1995 American Physical Society

We have searched for second-generation leptoquark (LQ) pairs in the &mgr;&mgr;+jets channel using 94+/-5 pb(-1) of &pmacr;p collider data collected by the D0 experiment at the Fermilab Tevatron during 1993-1996. No evidence for a signal is observed. These results are combined with those from the &mgr;nu+jets and nunu+jets channels to obtain 95% confidence level (C.L.) upper limits on the LQ pair production cross section as a function of mass and beta, the branching fraction of a LQ decay into a charged lepton and a quark. Lower limits of 200(180) GeV/c(2) for beta = 1(1 / 2) are set at the 95% C.L. on the mass of scalar LQ. Mass limits are also set on vector leptoquarks as a function of beta.

We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.

We present results from a search for anomalous WW and WZ production in ppbar collisions at sqrt(s) = 1.8 TeV. We used ppbar->evjjX events observed during the 1992-1993 run of the Fermilab Tevatron collider, corresponding to an integrated luminosity of 13.7 +- 0.7 pb^-1. A fit to the transverse momentum spectrum of the W boson yields direct limits on the CP-conserving anomalous WWgamma and WWZ coupling parameters of -0.9 < delta kappa < 1.1 (with lambda = 0) and -0.6 < lambda < 0.7 (with delta kappa = 0) at the 95% confidence level, for a form factor scale Lambda = 1.5 TeV, assuming that the WWgamma and WWZ coupling parameters are equal.

The Moon blocks cosmic rays, causing a deficit in their flux from its direction. Characterizing this Moon shadow is a technique used by cosmic ray air shower experiments to calibrate their angular resolution and validate the pointing accuracy. The GRAPES-3 air shower array, located in Ooty, India consists of an array of scintillator detectors and a large area muon telescope. It is sensitive to the measurement of cosmic ray and gamma ray induced showers in the TeV-PeV energy range. The timing measurements of the scintillator detectors were improved after upgrading the time-to-digital converters and coaxial cables in late 2012. The propagation delay of photomultiplier signal in coaxial cables were accurately determined on hourly basis using a random walk technique. The correction of shower front curvature for its dependence on the shower size and age together with accurate timing measurements led to a better angular resolution estimated using array division methods reported elsewhere [Jhansi et al., J. Cosmol. Astropart. Phys. 07 (2020) 024]. In this paper, we discuss the validation of the angular resolution by observing the shadow of the Moon in cosmic ray flux using 3 years (2014 to 2016) of air shower data recorded during the postupgrade period. The angular resolution of the array was estimated to be $0.83\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.09\ifmmode^\circ\else\textdegree\fi{}$ with a statistical significance of $9.1\ensuremath{\sigma}$ and pointing accuracy along the right ascension and declination directions were obtained to be $0.032\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.004\ifmmode^\circ\else\textdegree\fi{}$ and $0.09\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.003\ifmmode^\circ\else\textdegree\fi{}$ for showers of energy $&gt;5\text{ }\text{ }\mathrm{TeV}$, containing about 95% of triggered showers. The angular resolution improves to $0.38\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.06\ifmmode^\circ\else\textdegree\fi{}$ and $0.29\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.06\ifmmode^\circ\else\textdegree\fi{}$ for energy $&gt;100\text{ }\text{ }\mathrm{TeV}$ and $&gt;200\text{ }\text{ }\mathrm{TeV}$ respectively. The results are consistent with the values obtained from array division methods and are comparable to several air shower arrays that are located at almost twice the altitude of GRAPES-3. The improved angular resolution together with the accurate pointing increases the ability of GRAPES-3 to detect multi-TeV gamma ray sources.

Evidence of anomalous WW and WZ production was sought in pbar{p} collisions at a center-of-mass energy of sqrt(s) = 1.8 TeV. The final states $WW (WZ) to mu-nu-jet-jet + X, WZ to mu-nu-e-e + X and WZ to e-nu-e-e + X were studied using a data sample corresponding to an integrated luminosity of approximately 90 pb-1. No evidence of anomalous diboson production was found. Limits were set on anomalous WWgamma and WWZ couplings and were combined with our previous results. The combined 95% confidence level anomalous coupling limits for Lambda=2 TeV are -0.25 LE Delta-kappa LE 0.39 (lambda=0) and -0.18 LE lambda LE 0.19 (Delta \kappa = 0), assuming the WWgamma couplings are equal to the WWZ couplings.

We present limits on anomalous $\mathrm{WWZ}$ and $\mathrm{WW}\ensuremath{\gamma}$ couplings from a search for $\mathrm{WW}$ and $\mathrm{WZ}$ production in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$. We use $p\overline{p}\ensuremath{\rightarrow}e\ensuremath{\nu}\mathrm{jjX}$ events recorded with the D0 detector at the Fermilab Tevatron Collider during the 1992--1995 run. The data sample corresponds to an integrated luminosity of $96.0\ifmmode\pm\else\textpm\fi{}5.1{\mathrm{pb}}^{\ensuremath{-}1}$. Assuming identical $\mathrm{WWZ}$ and $\mathrm{WW}\ensuremath{\gamma}$ coupling parameters, the 95% C.L. limits on the $\mathrm{CP}$-conserving couplings are $\ensuremath{-}0.33&lt;\ensuremath{\lambda}&lt;0.36$ $(\ensuremath{\Delta}\ensuremath{\kappa}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0)$ and $\ensuremath{-}0.43&lt;\ensuremath{\Delta}\ensuremath{\kappa}&lt;0.59$ $(\ensuremath{\lambda}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0)$, for a form factor scale $\ensuremath{\Lambda}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.0\mathrm{TeV}$. Limits based on other assumptions are also presented.

We have searched for a heavy neutral gauge boson, Z′, using the decay channel Z′ → ee. The data were collected with the DØ detector at the Fermilab Tevatron during the 1992–1993 pp collider run at s=1.8 TeV from an integrated luminosity of 15±1 pb−1. Limits are set on the cross section times brancing ratio for the process pp → Z′ → ee as a function of the Z′ mass. We exclude the existence of a Z′ of mass less than 490 GeV/c2, assuming a Z′ with the same coupling strengths to quarks and leptons as the standard model Z boson.

We report on a search for pair production of a fourth generation charge −1/3 quark ( b′) in pp¯ collisions at s=1.8 TeV by the DØ experiment at the Fermilab Tevatron using an integrated luminosity of 93 pb−1. Both b′ quarks are assumed to decay via flavor changing neutral currents (FCNC). The search uses the signatures γ+3 jets +μ-tag and 2γ+2 jets. We see no significant excess of events over the expected background. We place an upper limit on the production cross section times branching fraction that is well below theoretical expectations for a b′ decaying exclusively via FCNC for b′ masses up to mZ+mb.Received 26 November 1996DOI:https://doi.org/10.1103/PhysRevLett.78.3818©1997 American Physical Society

We report a measurement of the differential cross section for W boson production as a function of its transverse momentum in proton–antiproton collisions at s=1.8 TeV. The data were collected by the DØ experiment at the Fermilab Tevatron Collider during 1994–1995 and correspond to an integrated luminosity of 85 pb−1. The results are in good agreement with quantum chromodynamics over the entire range of transverse momentum.

The ratio of the number of $W+1$ jet to $W+0$ jet events is measured with the D0 detector using data from the 1992--93 Tevatron Collider run. For the $W\ensuremath{\rightarrow}e\ensuremath{\nu}$ channel with a minimum jet ${E}_{T}$ cutoff of 25 GeV, the experimental ratio is $0.065\ifmmode\pm\else\textpm\fi{}0.003\left(\mathrm{stat}\right)\ifmmode\pm\else\textpm\fi{}0.007\left(\mathrm{syst}\right)$. Next-to-leading order QCD predictions for various parton distributions agree well with each other and are all over 1 standard deviation below the measurement. Varying the strong coupling constant ${\ensuremath{\alpha}}_{s}$ in both the parton distributions and the partonic cross sections simultaneously does not remove this discrepancy.

A search for narrow resonances that decay into tt pairs has been performed using 130 pb(-1) of data in the lepton + jets channel collected by the Dphi detector in pp collisions at square root of (s)=1.8 TeV. There is no significant deviation observed from the standard-model predictions at a top-quark mass of 175 GeV/c2. We therefore present upper limits at the 95% confidence level on the product of the production cross section and branching fraction to tt for narrow resonances as a function of the resonance mass MX. These limits are used to exclude the existence of a leptophobic top-color particle with mass MX<560 GeV/c2, using a theoretical cross section for a width GammaX=0.012MX.

We describe a measurement of the mass of the top quark from the purely hadronic decay modes of tt¯ pairs using all-jet data produced in pp¯ collisions at s=1.8TeV at the Fermilab Tevatron Collider. The data, which correspond to an integrated luminosity of 110.2±5.8pb−1, were collected with the DØ detector from 1992 to 1996. We find a top quark mass of 178.5±13.7(stat)±7.7(syst)GeV/c2.

The GRAPES-3 is a dense extensive air shower array operating with ∼400 scintillator detectors and it also contains a 560 m2 tracking muon detector (Eμ>1GeV), at Ooty in India. 25% of scintillator detectors are instrumented with two fast photomultiplier tubes (PMTs) for extending the dynamic range to ∼5×103 particles m−2. The scintillators, signal processing electronics and data recording systems were fabricated in-house to cut costs and optimize performance. The muon multiplicity distribution of the EAS is used to probe the composition of primary cosmic rays below the 'knee', with an overlap with direct measurements. Search for multi-TeV γ-rays from point sources is done with the aid of the muon detector. A good angular resolution of 0.7° at 30 TeV, is measured from the shadow of the Moon on the isotropic flux of cosmic rays. A sensitive limit on the diffuse flux of 100 TeV γ-rays is placed by using muon detector to filter the charged cosmic ray background. A tracking muon detector allows sensitive measurements on coronal mass ejections and solar flares through Forbush decrease events. We have major expansion plans to enhance the sensitivity of the GRAPES-3 experiment in the areas listed above.

The absence of a well established point source of very high energy (≳10TeV) γ-rays in the sky, makes the measurement of the angular resolution and the absolute pointing accuracy of an extensive air shower (EAS) array a challenging task. In the past, several groups have utilized the reduction in the isotropic flux of cosmic rays due to the shadows of the Moon and the Sun, to measure the angular resolution and the absolute pointing accuracy of their arrays. The data collected from the GRAPES-3 EAS array, over the period of 4 years from 2000 to 2003, has been used to observe the shadow of the Moon at a level of ∼5σ and that of the Sun at a lower level of significance. The high density of the detectors in GRAPES-3 enabled an angular resolution of 0.7° to be obtained at energies as low as 30 TeV. The angular resolution studies were further extended by using two other techniques, namely, the even–odd and the left–right methods. All three techniques have yielded nearly identical results on the energy dependent angular resolution.

A detailed description of a compact Monte Carlo simulation code "G3sim" for studying the performance of a plastic scintillator detector with wavelength shifter (WLS) fiber readout is presented. G3sim was developed for optimizing the design of new scintillator detectors used in the GRAPES-3 extensive air shower experiment. Propagation of the blue photons produced by the passage of relativistic charged particles in the scintillator is treated by incorporating the absorption, total internal, and diffuse reflections. Capture of blue photons by the WLS fibers and subsequent re-emission of longer wavelength green photons is appropriately treated. The trapping and propagation of green photons inside the WLS fiber is treated using the laws of optics for meridional and skew rays. Propagation time of each photon is taken into account for the generation of the electrical signal at the photomultiplier. A comparison of the results from G3sim with the performance of a prototype scintillator detector showed an excellent agreement between the simulated and measured properties. The simulation results can be parametrized in terms of exponential functions providing a deeper insight into the functioning of these versatile detectors. G3sim can be used to aid the design and optimize the performance of scintillator detectors prior to actual fabrication that may result in a considerable saving of time, labor, and money spent.

The space weather impacts propagation of galactic cosmic rays (CRs) in the heliosphere as explained by the diffusion-convection mechanism which predicts that the variation in CR intensity should be anticorrelated with changes in solar wind velocity (${\mathrm{V}}_{\mathrm{SW}}$). Several unrelated solar phenomena, including periodic ones such as 27 d solar rotation, annual, 11 yr solar activity, 22 yr solar magnetic cycle etc., and transient ones, for example, Forbush decreases (FDs), and ground level enhancements generally caused by solar flares or coronal mass ejections also affect CR intensity on Earth. These solar phenomena make a quantitative study of dependence of CR intensity on ${\mathrm{V}}_{\mathrm{SW}}$ rather difficult. Here, the high statistics muon data of six years (2000--2005) from the large GRAPES-3 muon telescope have been used to study the correlation between ${\mathrm{V}}_{\mathrm{SW}}$ and CR intensity. Data gathered during these six years were used after minimizing the contribution of various unrelated solar phenomena outlined above. We observed a strong anticorrelation between the variations in ${\mathrm{V}}_{\mathrm{SW}}$ and CR intensity at a significance of $19\ensuremath{\sigma}$.

Abstract The CMS experiment at the CERN LHC will be upgraded to accommodate the 5-fold increase in the instantaneous luminosity expected at the High-Luminosity LHC (HL-LHC) [1]. Concomitant with this increase will be an increase in the number of interactions in each bunch crossing and a significant increase in the total ionising dose and fluence. One part of this upgrade is the replacement of the current endcap calorimeters with a high granularity sampling calorimeter equipped with silicon sensors, designed to manage the high collision rates [2]. As part of the development of this calorimeter, a series of beam tests have been conducted with different sampling configurations using prototype segmented silicon detectors. In the most recent of these tests, conducted in late 2018 at the CERN SPS, the performance of a prototype calorimeter equipped with ≈12,000 channels of silicon sensors was studied with beams of high-energy electrons, pions and muons. This paper describes the custom-built scalable data acquisition system that was built with readily available FPGA mezzanines and low-cost Raspberry Pi computers.

We report on a search for R-parity violating supersymmetry in p-pbar collisions at sqrt(s) = 1.8 TeV using the D0 detector at Fermilab. Events with at least two electrons and four or more jets were studied. We observe 2 events in 99 +- 4.4 pb-1 of data, consistent with the expected background of 1.8 +- 0.4 events. This result is interpreted within the framework of minimal low-energy supergravity supersymmetry models. Squarks with mass below 243 GeV/c^2 and gluinos with mass below 227 GeV/c^2 are excluded at the 95% confidence level (C. L.) for A_0=0, mu &lt; 0$, tan beta=2 and a finite value for R-parity violating Yukawa coupling lambda'_1jk (j=1, 2 and k=1, 2, 3). For equal squark and gluino masses, the corresponding mass limit is 277 GeV/c^2.