R. Tanaka

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of $\sqrt{s}=7\ \mathrm{TeV}$ corresponding to an integrated luminosity of 38 pb−1. Jets are reconstructed with the anti-k t algorithm with distance parameters R=0.4 or R=0.6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta p T≥20 GeV and pseudorapidities |η|<4.5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2.5 % in the central calorimeter region (|η|<0.8) for jets with 60≤p T<800 GeV, and is maximally 14 % for p T<30 GeV in the most forward region 3.2≤|η|<4.5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon p T, the sum of the transverse momenta of tracks associated to the jet, or a system of low-p T jets recoiling against a high-p T jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-p T jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined.

A search for doubly-charged Higgs bosons decaying to pairs of electrons and/or muons is presented. The search is performed using a data sample corresponding to an integrated luminosity of 4.7 fb-1 of pp collisions at sqrt(s) = 7 TeV collected by the ATLAS detector at the LHC. Pairs of prompt, isolated, high-pT leptons with the same electric charge (ee, emu, mumu) are selected, and their invariant mass distribution is searched for a narrow resonance. No significant excess over Standard Model background expectations is observed, and limits are placed on the cross section times branching ratio for pair production of doubly-charged Higgs bosons. The masses of doubly-charged Higgs bosons are constrained depending on the branching ratio into these leptonic final states. Assuming pair production, coupling to left-handed fermions, and a branching ratio of 100% for each final state, masses below 409 GeV, 375 GeV, and 398 GeV are excluded for ee, emu, mumu, respectively.

This Report summarizes the results of the first 10 months' activities of the LHC Higgs Cross Sections Working Group. The main goal of the working group was to present the status-of-art on Higgs Physics at the LHC integrating all new results that have appeared in the last few years. The Report is more than a mere collection of the proceedings of the general meetings. The subgroups have been working in different directions. An attempt has been made to present the first Report from these subgroups in a complete and homogeneous form. The subgroups' contributions correspondingly comprise the main parts of the Report. A significant amount of work has been performed in providing higher-order corrections to the Higgs-boson cross sections and pinning down the theoretical uncertainty of the Standard Model predictions. This Report comprises explicit numerical results on total cross sections, leaving the issues of event selection cuts and differential distributions to future publications. The subjects for further study are identified.

Measurements are presented of differential cross-sections for top quark pair production in pp collisions at sqrt(s) = 7 TeV relative to the total inclusive top quark pair production cross-section. A data sample of 2.05/fb recorded by the ATLAS detector at the Large Hadron Collider is used. Relative differential cross-sections are derived as a function of the invariant mass, the transverse momentum and the rapidity of the top quark pair system. Events are selected in the lepton (electron or muon) + jets channel. The background-subtracted differential distributions are corrected for detector effects, normalized to the total inclusive top quark pair production cross-section and compared to theoretical predictions. The measurement uncertainties range typically between 10% and 20% and are generally dominated by systematic effects. No significant deviations from the Standard Model expectations are observed.

The production of a [Formula: see text] boson in association with a [Formula: see text] meson in proton-proton collisions probes the production mechanisms of quarkonium and heavy flavour in association with vector bosons, and allows studies of multiple parton scattering. Using [Formula: see text] of data collected with the ATLAS experiment at the LHC in [Formula: see text] collisions at [Formula: see text], the first measurement of associated [Formula: see text] production is presented for both prompt and non-prompt [Formula: see text] production, with both signatures having a significance in excess of [Formula: see text]. The inclusive production cross-sections for [Formula: see text] boson production (analysed in [Formula: see text] or [Formula: see text] decay modes) in association with prompt and non-prompt [Formula: see text] are measured relative to the inclusive production rate of [Formula: see text] bosons in the same fiducial volume to be [Formula: see text] and [Formula: see text] respectively. Normalised differential production cross-section ratios are also determined as a function of the [Formula: see text] transverse momentum. The fraction of signal events arising from single and double parton scattering is estimated, and a lower limit of [Formula: see text] at [Formula: see text] confidence level is placed on the effective cross-section regulating double parton interactions.

A search for pair-produced massive coloured scalar particles decaying to a four-jet final state is performed by the ATLAS experiment at the LHC in proton–proton collisions at $\sqrt{s} = 7\ \mbox{TeV}$ . The analysed data sample corresponds to an integrated luminosity of 4.6 fb−1. No deviation from the Standard Model is observed in the invariant mass spectrum of the two-jet pairs. A limit on the scalar gluon pair production cross section of 70 pb (10 pb) is obtained at the 95 % confidence level for a scalar gluon mass of 150 GeV (350 GeV). Interpreting these results as mass limits on scalar gluons, masses ranging from 150 GeV to 287 GeV are excluded at the 95 % confidence level.

A search for heavy long-lived charged R-hadrons is reported using a data sample corresponding to 3.2 fb−1 of proton–proton collisions at s=13TeV collected by the ATLAS experiment at the Large Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow propagation velocities, which are signatures of heavy charged particles travelling significantly slower than the speed of light. No significant deviations from the expected background are observed. Upper limits at 95% confidence level are provided on the production cross section of long-lived R-hadrons in the mass range from 600 GeV to 2000 GeV and gluino, bottom and top squark masses are excluded up to 1580 GeV, 805 GeV and 890 GeV, respectively.

This Report summarizes the results of the first 10 months' activities of the LHC Higgs Cross Sections Working Group. The main goal of the working group was to present the status-of-art on Higgs Physics at the LHC integrating all new results that have appeared in the last few years. The Report is more than a mere collection of the proceedings of the general meetings. The subgroups have been working in different directions. An attempt has been made to present the first Report from these subgroups in a complete and homogeneous form. The subgroups' contributions correspondingly comprise the main parts of the Report. A significant amount of work has been performed in providing higher-order corrections to the Higgs-boson cross sections and pinning down the theoretical uncertainty of the Standard Model predictions. This Report comprises explicit numerical results on total cross sections, leaving the issues of event selection cuts and differential distributions to future publications. The subjects for further study are identified.

The results of a search for the production of second generation scalar leptoquarks are presented for final states consisting of either two oppositely charged muons and at least two jets or a muon plus missing transverse momentum and at least two jets. A total of 1.03/fb integrated luminosity of proton-proton collision data produced by the Large Hadron Collider at sqrt(s) = 7 TeV and recorded by the ATLAS detector is used for the search. The event yields in the signal regions are found to be consistent with the Standard Model background expectations. The production of second generation leptoquarks is excluded for a leptoquark mass m_LQ < 594 (685) GeV at 95% confidence level, for a branching ratio of 0.5 (1.0) for leptoquark decay to a muon and a quark.

A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 3779 (2001)]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy bandwidth. Experimental results from the ATF2 accelerator at KEK are presented that validate the operating principle of such a scheme by demonstrating the demagnification of a 1.3 GeV electron beam down to below 65 nm in height using an energy-scaled version of the compact focusing optics designed for the ILC collider.Received 10 September 2013DOI:https://doi.org/10.1103/PhysRevLett.112.034802© 2014 American Physical Society

The total cross section for the process of the e+e- annihilation into hadrons has been measured at the centre-of-mass energies of 50 GeV and 52 GeV and a search has been made for new heavy quarks. The ratios R = σ(e+e- → hadrons)/σpoint(e+e- → μ+μ-) obtained are 4.4±0.5 at 50 GeV and 4.7±0.3 at 52 GeV, respectively. An additional systematic uncertainty is 10%. From the event shape analysis we found no evidence for a new quark with charge 23e.

We present results of an experimental study of e+e−+ hadrons in the kinematic regime for which the process is interpreted as hadron production in collisions of almost-real photons. The data sample corresponds to an integrated luminosity of 27.5 pb− and covers center-of-mass energies from 55 to 61.4 GeV. We observe more events than expected from the incoherent sum of quark-parton and vector-meson-dominance models, and we give a quantitative explanation of the excess by including the hard scattering of the hadronic constituents of the photons calculated with QCD.

This paper presents a search for Higgs bosons decaying to four leptons, either electrons or muons, via one or two light exotic gauge bosons ${Z}_{d}$, $H\ensuremath{\rightarrow}Z{Z}_{d}\ensuremath{\rightarrow}4\ensuremath{\ell}$ or $H\ensuremath{\rightarrow}{Z}_{d}{Z}_{d}\ensuremath{\rightarrow}4\ensuremath{\ell}$. The search was performed using $pp$ collision data corresponding to an integrated luminosity of about $20\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ at the center-of-mass energy of $\sqrt{s}=8\text{ }\text{ }\mathrm{TeV}$ recorded with the ATLAS detector at the Large Hadron Collider. The observed data are well described by the Standard Model prediction. Upper bounds on the branching ratio of $H\ensuremath{\rightarrow}Z{Z}_{d}\ensuremath{\rightarrow}4\ensuremath{\ell}$ and on the kinetic mixing parameter between the ${Z}_{d}$ and the Standard Model hypercharge gauge boson are set in the range $(1--9)\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}5}$ and $(4--17)\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}2}$ respectively, at 95% confidence level assuming the Standard Model branching ratio of $H\ensuremath{\rightarrow}Z{Z}^{*}\ensuremath{\rightarrow}4\ensuremath{\ell}$, for ${Z}_{d}$ masses between 15 and 55 GeV. Upper bounds on the effective mass mixing parameter between the $Z$ and the ${Z}_{d}$ are also set using the branching ratio limits in the $H\ensuremath{\rightarrow}Z{Z}_{d}\ensuremath{\rightarrow}4\ensuremath{\ell}$ search, and are in the range $(1.5--8.7)\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}4}$ for $15&lt;{m}_{{Z}_{d}}&lt;35\text{ }\text{ }\mathrm{GeV}$. Upper bounds on the branching ratio of $H\ensuremath{\rightarrow}{Z}_{d}{Z}_{d}\ensuremath{\rightarrow}4\ensuremath{\ell}$ and on the Higgs portal coupling parameter, controlling the strength of the coupling of the Higgs boson to dark vector bosons are set in the range $(2--3)\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}5}$ and $(1--10)\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}4}$ respectively, at 95% confidence level assuming the Standard Model Higgs boson production cross sections, for ${Z}_{d}$ masses between 15 and 60 GeV.

We present cross section measurements for inclusive jet production in almost-real photon-photon interactions at TRISTAN using the AMY detector. The results are compared with leading-order QCD calculations for different parameterizations of the parton density in the photon.

The total cross section for e+e− annihilation into hadrons has been measured for CM energies ranging from 50 to 57 GeV. We fit the predictions of the standard model to these measurements and those at lower energies. The mass of the Z0 boson, MZ, and the QCD scale parameter, ΛMS, are derived from the fit. The results are MZ=88.6−1.8+2.0 GeV/c2, and ΛMS=0.15−0.11+0.16 GeV.

We accumulated e+e− annihilations into multi-hadrons at CM energies between 54.0 and 61.4 GeV with the VENUS detector at TRISTAN. Measured R-ratios are consistent with the standard model using the Z-boson mass; 91.1 GeV/c2. Using two new observables, we searched for a planar four-jet and other multi-jet events resulting from the decay of a charge — 13eb' quark. Having observed no positive signals, we excluded b' masses between 19.4 and 28.2 GeV/c2 with a 95% confidence level, regardless of branching into charged current and loop-induced flavor-changing neutral current decay, including a possible Higgs decay process. The charge +23e top quark was excluded below f30.2 GeV/c2.

Measurements of the differential cross sections for e+e−→μ+μ− and e+e−→τ+τ− at values of s from 52 to 57 GeV are reported. The forward-backward asymmetries and the total cross sections for these reactions are found to be in agreement with predictions of the standard model of the electro-weak interactions. These measurements are used to extract values of the weak coupling constant gvegvl and gAegAl, where l = μ or τ.

The ratio $R$ of the total cross section for ${e}^{+}{e}^{\ensuremath{-}}$ annihilation into hadrons to the lowest-order QED cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ has been measured for center-of-mass energies ranging from 50 to 61.4 GeV. If we allow for an overall shift of ---4.9%, about 1.5 times our estimated normalization error, the results are consistent with the standard-model predictions.

We studied radiation tolerance of pn junction 6H-SiC (silicon carbide) diodes on electrical properties and detector performance for alpha particles. Three pn-SiC diodes were irradiated with gamma-rays at doses (60Co source) up to 2.5 MGy and two diodes were irradiated with beta-rays (2 MeV) at fluences up to 1×1015 electrons/cm2. The ideality factors η, which are estimated from current–voltage (I–V) characteristics of diodes, were around 2.0 for all diodes, and no significant change in η was observed after both gamma and beta irradiations. The leakage currents increase with gamma doses up to range of 0.4–1.5 MGy and decrease with gamma doses above 1.5 MGy. For beta-rays, a little increase in leakage current was observed due to irradiation. The depletion layer width W was estimated from capacitance–voltage (C–V) characteristics of diodes. The W at several reverse bias voltage increases with increasing both gamma doses and beta fluences. The detector performance was examined by using alpha particles of two different energies, 4.3 and 1.8 MeV.For 1.8 MeV alpha particles, a charge collection efficiency, CCE, of 100% were demonstrated at reverse biases above 20 V, even after the irradiation at gamma doses up to 2.5 MGy.

The relative production ratio of 3-jet events to the total number of hadronic events was studied in e+e− annihilations at centre-of-mass energies between 54 and 61.4 GeV. The QCD scale parameter has been determined to be ΛMS=254−47+55±56 MeV on the basis of a QCD cascade with the next-to-leading logarithmic approximation.

New metastable massive particles with electric and colour charge are features of many theories beyond the Standard Model. A search is performed for long-lived gluino-based R-hadrons with the ATLAS detector at the LHC using a data sample corresponding to an integrated luminosity of 31 pb−1. We search for evidence of particles that have come to rest in the ATLAS detector and decay at some later time during the periods in the LHC bunch structure without proton–proton collisions. No significant deviations from the expected backgrounds are observed, and a cross-section limit is set. It can be interpreted as excluding gluino-based R-hadrons with masses less than 341 GeV at the 95 % C.L., for lifetimes from 10−5 to 103 seconds and a neutralino mass of 100 GeV.

This Report summarises the results of the second year's activities of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. The first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) focuses on predictions (central values and errors) for total Higgs production cross sections and Higgs branching ratios in the Standard Model and its minimal supersymmetric extension, covering also related issues such as Monte Carlo generators, parton distribution functions, and pseudo-observables. This second Report represents the next natural step towards realistic predictions upon providing results on cross sections with benchmark cuts, differential distributions, details of specific decay channels, and further recent developments.

Results from an extensive study of nonprojective Shashlik calorimeter prototypes are reported. Nine (47 × 47 mm2) towers were exposed to a high energy electron beam at CERN SPS and read out by silicon photodiodes followed by low noise preamplifiers. The main results are the measurements of the energy and shower position resolution and the angular resolution of the electron shower direction. The shower direction measurement is encouraging being in agreement at the tower center with a resolution of σθ(mrad) = 70/√E (10 mrad for 50 GeV electrons). The uniformity of the calorimeter response is found to be better than ± 1%. The mean light yield measured in Shashlik towers equipped with Kuraray Y7 WLS fibres and aluminized at the front end of the tower is of the order of 13 photons/MeV.

QED processes up to O(α4) have been studied at center-of-mass energies between 50 and 57 GeV using the AMY detector at TRISTAN. A possible substructure of the electron and muon is investigated in terms of chiral invariant contact interactions and also in terms of excited lepton production. The differential cross section data for e+e−→e+e− are consistent with the standard model at a confidence level of only 3.5%. From the absence of excited lepton production, we establish new upper limits on the coupling to excited electrons of mass up to 56 GeV/c2 and on the coupling to excited muons of mass up to 52 GeV/c2.

Correlations among identically charged pions were measured for pions produced inp p collisions at 360 GeV/c using the EHS spectrometer. The effective radius for pion production was determined to be 1.02±0.20 fm with a chaoticity factor 0.32±0.08. We attempted to obtain the radii in the directions parallel and perpendicular to the beam axis and found no difference between them. No multiplicity dependence of the radius was observed at this energy. A peak near zero in the four momentum transfer distribution showed significant deviation from a single Gaussian. The results of an analysis of the three like pion enhancement were consistent with those for two pions.

A search for sequential charged leptons decaying into massive neutrinos has been performed at ${E}_{\mathrm{c}.\mathrm{m}.}=56$ GeV at the KEK colliding-beam accelerator TRISTAN. We have found no evidence for the production of the charged heavy leptons for an integrated luminosity of 5.3 ${\mathrm{pb}}^{\ensuremath{-}1}$. A search for stable charged leptons was also conducted yielding null results. A new mass limit on the charged heavy leptons was obtained as a function of the mass of the associated neutrinos.

We have tested extra Z models in the reactions e+e−→μ+μ−, τ+τ− and hadrons in the energy range 50<s<64GeV using the VENUS detector at the TRISTAN e+e− storage ring. Our data are in good agreement with the standard model prediction (χ2NDf=2.931)). We have obtained 90% confidence-level lower limits of 105, 125 and 231 GeV for the masses of ZΨ, Zη and Zχ bosons which are expected from the E6 grand unified theory. We also place a 90% confidence-level lower limit of 426 GeV for the mass of an extra-Z boson whose couplings to quarks and leptons are assumed to be the same as those for the standard Z boson. Our results exceed the previous experimental limits from the pp collider experiments, although there have been some combined analyses reporting the limits better than those obtained in the present analysis.

Using 123 multihadronic inclusive muon-production ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ annihilation events at an average c.m. energy of 55.2 GeV, we extracted the forward-backward charge asymmetry of the ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}bb\ifmmode\bar\else\textasciimacron\fi{} process and the R ratio for bb\ifmmode\bar\else\textasciimacron\fi{} production. We used an analysis method in which the behavior of the c quark and lighter quarks is assumed, with only that of the b quark left indeterminate. The results, ${A}_{b}$=-0.72\ifmmode\pm\else\textpm\fi{}0.28(stat)\ifmmode\pm\else\textpm\fi{}0.13(syst) and ${R}_{b}$=0.57\ifmmode\pm\else\textpm\fi{}0.16\ifmmode\pm\else\textpm\fi{}0.10, are consistent with the standard model.

We applied the surface build-up Cu-polyimide flex-circuit technology with laser vias to the ATLAS SCT barrel hybrid to be made in one piece from the connector to the electronics sections including cables. The hybrids, reinforced with carbon–carbon substrates, provide mechanical strength, thermal conductivity, low-radiation length, and stability in application-specific integrated circuit (ASIC) operation. By following the design rules, we experienced little trouble in breaking the traces. The pitch adapter between the sensor and the ASICs was made of aluminum traces on glass substrate. We identified that the generation of whiskers around the wire-bonding feet was correlated with the hardness of metallized aluminum. The appropriate hardness has been achieved by keeping the temperature of the glasses as low as room temperature during the metallization. The argon plasma cleaning procedure cleaned the contamination on the gold pads of the hybrids for successful wire bonding, although it was unsuccessful in the aluminum of the pitch adapters.

By studying ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ annihilations in the center-of-mass energy range between 50 and 60.8 GeV, we have established a 95%-confidence-level lower limit on the mass of a fourth-generation charge -(1/3 quark b' of 27.2 GeV. In contrast with all previous searches, this limit has been obtained through consideration of the decay processes b'\ensuremath{\rightarrow}b\ensuremath{\gamma} and b'\ensuremath{\rightarrow}bg aswell as b'\ensuremath{\rightarrow}${\mathrm{cW}}^{\mathrm{\ensuremath{-}}}$. For the cases where any one of the three decay modes dominates, we obtain higher mass limits.

The forward-backward asymmetry of quarks produced in ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ annihilations, summed over all flavors, is measured at \ensuremath{\surd}s between 50 and 60.8 GeV. Methods of determining the charge direction of jet pairs are discussed. The asymmetry is found to agree with the five-flavor standard model.

Nonirradiated and irradiated ATLAS silicon microstrip barrel and endcap modules have been beamtested with 4-GeV/c pions. Pulse shapes confirmed the peaking time of the amplifier to be 22 ns with slight deterioration in the irradiated modules. Median charges saturated around 3.8 fC, both in the nonirradiated and the irradiated modules. Signal/noise ratios, using the noise estimates from the in-situ calibration, were >16 in the nonirradiated (>150 V) and >10 in the irradiated (>300 V) barrel modules. No excess common-mode noise was observed.

More than 2000 silicon modules need to be placed and fastened on the ATLAS SCT barrel tracker. A semi-automatic pick-and-place work robot was designed and developed to cope with the module placement for the SCT barrel assembly. We found that this robot could place modules to a mechanical precision of better than 25 μm.

Abstract A new silicon microstrip detector was designed by the CDF collaboration for the proposed high-luminosity operation of the Tevatron p p ¯ collider (Run IIb). The detector is radiation-tolerant and will still be functional after exposure to particle fluences of 10 14 1 - MeV equivalent neutrons / cm 2 and radiation doses of 20 MRad. The detector will maintain or exceed the performance of the current CDF silicon detector throughout Run IIb. It is based on an innovative silicon “supermodule” design. Critical detector components like the custom radiation-hard SVX4 readout chip, the beryllia hybrids and mini-port (repeater) cards, and the silicon sensors fulfill their specifications and were produced with high yields. The design goals and solutions of the CDF Run IIb silicon detector are described, and the performance of preproduction modules is presented in detail. Results relevant for the development of future silicon systems are emphasized.

A result of the search for the top quark in e + e - annihilation into hadrons at \(\sqrt{s}=50\) GeV is presented. The experiment has been perforrnxed using the VENUS detector at TRISTAN. No evidence has been found for the production of the top quark. From the study using the event shape of the multihadron events, the upper limit of the production cross section is found to be 16 pb at thcc 95% confidence level.

A study of single photon events, produced in association with light neutrinos or other weakly interacting neutral particlaes in e+e− collisions, has been performed at √s=54.0–61.4 GeV with the VENUS detector at TRISTAN. No anomalous signal has been observed in a data sample corresponding to an integrated luminosity of 28.2 pb−1. This result indicates that the upper limit on the number of light neutrinos, Nν, is 11 (15) at a 90 (95)% confidence level. Combining this with published results from other e+e− experiments, the number of light neutrinos is limited to Nν<3.9(4.8) at the 90 (95)% confidence level. Limits are also placed on the mass of supersymmetric particles.

A charge asymmetry has been measured in hadron jets from e+e− annihilation at energies between 52 and 61.4 geV (〈√s〉=57.6 GeV). The measured asymmetry is A=11.4%±2.2%±2.1% and is consistent with the prediction of the standard model of the electroweak theory. By using the differential cross section, lower limits of the compositeness scale in eeqq contact interactions have been determined to be typically a few TeV at 95% CL.

A data acquisition system for the VENUS detector at the TRISTAN electron-positron collider is presented. The whole system of the VENUS detector consists of nine different kinds of principal detectors, and the total number of electronics channels of the system reaches about 30 000. A FASTBUS system was introduced as the main data path and the TKO and the CAMAC standard have also been utilized for the frontend electronics. A FASTBUS interface to an on-line computer (VAX11/780), simplex segment interconnect and many data acquisition modules were developed. Most of the data are analyzed in a VAX cluster system in real time. Data logging is done in a main frame computer (FACOM M382) by using an automatic loading cartridge tape subsystem.

As a part of the quality assurance procedure of the ATLAS SCT (Semiconductor Tracker) barrel modules, the response of the microstrip detector is measured by injecting focused Nd:YAG laser at each strip. The test is sensitive to sensor originated problems and a cross check to the results obtained from the electrical tests performed with the test pulse system implemented in the readout ASICs. Combining these results with the probing results obtained by the silicon sensor manufacturer, we verified the reliabilities of these tests and classified the type of defects for overall performance evaluation of the modules.

We present a quantitative study on sensitivities to the top-decay anomalous couplings, taking into account realistic experimental conditions expected at Tevatron and LHC. A double angular distribution of $W$ and charged lepton in the top-decay is analyzed, using $t\overline{t}$ events in the $\mathrm{\text{leptons}}+\mathrm{\text{jets}}$ channel. In order to improve sensitivities to the anomalous couplings, we apply two techniques: (i) We use a likelihood fitting method for full kinematical reconstruction of each top event. (ii) We develop a new effective spin reconstruction method for leptonically-decayed top quarks; this method does not require spin information of the antitop side. For simplicity, we neglect couplings of right-handed bottom quark as well as $CP$ violating couplings. The 95% C.L. estimated bound on a ratio of anomalous couplings reads $\ensuremath{-}0.81&lt;{f}_{2}/{f}_{1}&lt;\ensuremath{-}0.70$, $\ensuremath{-}0.12&lt;{f}_{2}/{f}_{1}&lt;0.14$ using 1000 reconstructed top events at Tevatron, while $\ensuremath{-}0.74&lt;{f}_{2}/{f}_{1}&lt;\ensuremath{-}0.72$, $\ensuremath{-}0.01&lt;{f}_{2}/{f}_{1}&lt;0.01$ is expected with 100 k reconstructed top events at LHC, where only statistical errors are taken into account. A two-fold ambiguity in the allowed range remains when the number of events exceeds a few hundred.

The differential cross sections for e + e - → e + e - and e + e - →γγ have been measured at the highest energy of \(\sqrt{s}=52\) GeV in e + e - collisions.The process e + e - → e + e - is well understood within the framework of the standard model of electroweak interactions. The reaction e + e - →γγ is found to be in good agreement with QED. The 95% confidence limits obtained for the QED cut-off parameters are \(\varLambda_{+}>61\) GeV and \(\varLambda_{-}>72\) GeV for e + e - →γγ.

Abstract Using the single ion hit Transient Ion Beam Induced Current (TIBIC), the transient current generated in n + p 6H–SiC diodes by 15 MeV-oxygen (O 4+ ) microbeams was measured. The signal peak of the transient current increases, and the fall-time, which is defined as the decay time from 90% to 10% of the transient current, decreases with increasing applied reverse bias. The charge generated in n + p 6H–SiC diodes was estimated from the integration of the TIBIC signal. As the result, the value of collected charge increases with increasing applied reverse bias up to 90 V, and the saturation of the collected charge was observed at reverse biases above 100 V. At reverse biases below 110 V, the charge generated in the deeper region as compared to the depletion layer length is collected due to the funneling effect. Almost all charge generated in n + p SiC diodes by 15 MeV-O 4+ irradiation can be collected when the length of depletion layer becomes longer than the projection range of 15 MeV-O 4+ ions. No significant difference in transient behavior and charge collection is observed between gamma-ray (0.26 MGy) irradiated and non-irradiated samples.

Measurements of open charm production in photon-photon collisions made with the AMY detector at TRISTAN are reported. Charmed hadrons were identified by detecting the high momentum muons or electrons from their semileptonic decays. The data sample corresponds to an integrated luminosity of 275 pb−1 at an average center of mass energy of 58 GeV. Results are presented in the form of cross sections of inclusive leptons from charm for both muons and electrons. The measured cross section is 1.8 standard deviations higher than theoretical predictions based on the direct and photon-gluon fusion process, where the mass of charm quark is assumed to be 1.6 GeV.

Using e+e− annihilation events accumulated with the AMY detector at the TRISTAN collider, we have studied the Bose-Einstein correlations in the distributions of like-sign charged tracks. As reference samples we used the opposite-sign charged track pairs and mixed pairs, which are like-sign pairs synthesized from tracks belonging to different events. The results of the different reference samples give approximately 0.45 for the correlation strength and approximately 0.65 fm for the source size. Previous measurements of these parameters in e+e− annihilation at energies from CESR to LEP show remarkably flat dependence on s. Our results conform well with this picture.

We report results of a study of four-lepton final states produced in e+e− collisions at center-of-mass energies from 50 to 61.4 GeV using the AMY detector at the TRISTAN collider. For the cases where two or three charged tracks are produced at large angles relative to the beam direction, the cross sections agree with QED. However, we observe an excess of e+e−→e+e−μ+μ− events with four tracks at wide angles and with dimuon mass less than 1.0 GeV/c2.

A search for pair production of fourth-generation sequential leptons in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at a center-of-mass energy $\sqrt{s}=56$ GeV is reported. Event topologies corresponding to the cases where one particle decays leptonically while the other decays hadronically as well as those where both particles decay hadronically were explored. We set a 95%-confidence-level lower limit of 27.6 GeV/${\mathit{c}}^{2}$ for the mass of a fourth-generation lepton.

We have developed a semi-automated assembly system and constructed 124 silicon microstrip modules so far for the ATLAS SCT barrel. This article describes the assembly procedure, evaluations of precisions and the module survey results. A precision of ∼2 μm is achievable with this assembly system.

Fermilab plans to deliver 5–15 fb−1 of integrated luminosity to the CDF and D0 experiments. The current inner silicon detectors at CDF (SVXIIa and L00) will not tolerate the radiation dose associated with high-luminosity running and will need to be replaced. A new readout chip (SVX4) has been designed in radiation-hard 0.25 μm, CMOS technology. Single-sided sensors are arranged in a compact structure, called a stave, with integrated readout and cooling systems. This paper describes the general design of the Run IIb system, testing results of prototype electrical components (staves), and prototype silicon sensor performance before and after irradiation.

The charge generated in 6H-SiC n+p diodes by gold (Au) ion irradiation at an energy of 12 MeV was evaluated using the Transient Ion Beam Induced Current (TIBIC). The signal peak of the transient current increases, and the fall-time decreases with increasing applied reverse bias. The value of collected charge experimentally obtained is smaller than the ideal value. The Charge Collection Efficiency (CCE) of 6H-SiC n+p diodes irradiated with Au ions is approximately 50 % in spite that the CCE of 100 % is obtained in the case of oxygen (O) ion irradiation.

We present a study of the third moment of the inclusive momentum distribution of particles within jets produced by e+ e- annihilation at TRISTAN. In this analysis, the QCD coupling strength αs is determined by fits to the prediction of the Next-to-Leading Logarithm Parton-Shower model. The measured value of αs(57.9 GeV) = 0.134-0.005+0.006.

A search for a new charge -(1/3 quark has been carried out at the KEK ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$Collider TRISTAN under the assumption of its photonic decay through a flavor-changing neutral current (FCNC). The observed number of multihadronic events with isolated photons is consistent with that expected from the known five quark flavors. Including the usual charged-current decays, limits on the absolute photonic branching ratio and FCNC processes were obtained.

New readout electronics for the Venus end-cap liquid argon calorimeter was developed and has been operating for over a year at TRISTAN. The entire system was designed in such a way that the gain of each readout channel could be calibrated to better than 1%. The system consists of 3840 channels of readout electronics. It uses hybrid charge-sensitive amplifiers located in the 7.5-kG magnetic field and TKO-bus-based electronics which consists of CR-(RC)/sup 4/ filters, sample-and-hold circuits and 14-bit ADCs (analog digital converters). The energy resolution sigma /sub E//E for an electromagnetic shower has been found to be 3.5% at 28 GeV without any channel-by-channel gain calibration. The resolution was also determined to be sigma E/E=1.4%+11.3%/ square root E(GeV) from a large sample of 28-GeV Bhabha events and a small sample of e/sup +/e/sup -/ to e/sup +/e/sup -/ gamma events.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

With data corresponding to 142 pb−1 accumulated at s = 57.8 GeV by the AMY detector at TRISTAN we measure the cross section of the reactions e+e− → μ+μ− and e+e− → τ+τ− and the symmetry in the angular distributions. For the lowest order cross section we obtain σμμ = 27.54 ± 0.65 ± 0.95 pb and σττ = 28.27 ± 0.87 ± 0.69 pb, and for the forward-backward asymmetry, Aμμ = 0.303 ± 0.027 ± 0.008 and Aττ = −0.291 ± 0.040 ± 0.019. These measurements agree with the standard model. Assuming e−μ−τ univrsality we extract the vector and axial coupling constants | gν| = 0.00 ± 0.09 and |gA| = 0.476 ± 0.024. A fit of data to composite models places lower bounds (95% confidence level) on the compositeness scale of 2–4 TeV.

New projective prototypes of a scintillator/lead sandwich type sampling calorimeter Shashlik with a silicon preshower detector have been constructed and tested with an electron beam at CERN-SPS. The energy resolution is measured to be 8.7%E(GeV) in stochastic term, 0.330/E(GeV) in noise term and 0.5% in constant term. The angular resolution is better than 70 mradE(GeV).

A search for a fourth-generation quark with \ensuremath{\Vert}Q\ensuremath{\Vert}=e/3 has been made with the VENUS detector at the KEK ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ collider TRISTAN. Multihadron events with a spherical shape or containing isolated leptons were studied. There is no evidence for an excess production of such events in ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ collision at \ensuremath{\surd}s =56--57 GeV and a lower limit on the mass is 27.5 GeV/${c}^{2}$ at the 95% C.L.

Abstract Temperature dependence of forward I‐V properties in SiC pin diodes with relatively low sustaining voltage is investigated. Decrease of forward voltage and differential resistance with increase of temperature is characterized by device simulation considering stacking faults. Band structure in stacking faults is suggested to be type‐I quantum well due to strain by the difference of lattice interval in basal plane. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

A wind turbine installed in winter lightning areas is required to be equipped with a detection system that can accurately detect a lightning strike. The lighting detection systems using a large-diameter Rogowski coil with high measurement accuracy are widely used, but it is expensive and costs more than one million yen per unit. In this paper, we report the result of the frequency characteristic measurement of the self-made lightning detection system using a large-diameter Rogowski. The system is manufactured at a low cost, is cheaper than the currently popular large-diameter Rogowski coil type lightning detection system.

In high energy physics, the measurement of APD's excess noise factor is essentially made by histogram method. Another method used mainly in telecommunication field is to measure the noise spectral density using a transresistance amplifier from which the output signal is analysed by FFT (Fast Fourier Transform). The main advantage of this spectral method is the capability to separate the different domain of the whole noise spectrum. In addition, it is easy to use and is more sensitive at low bias voltage. This method also allows one to detect the generation and recombination noises if they exist. For certain type of APDs, this method gives an opportunity to measure the primary photocurrent. We have measured the excess noise of two types of APDs with this spectral method as well as histogram method. The result by the spectral method coincides well with the histogram method.

Prototypes of ATLAS-SCT modules with ABCD readout chips were tested in a 4 GeV/c pion beam at KEK's proton synchrotron. Of both SCT module geometries—barrel and forward—three identical modules were placed in the beam. One module of each type had been irradiated to 3×1014 protons/cm2 in the CERN PS previous to the beam test. A method has been developed to reconstruct the time-resolved shaper pulse from the binary hit information, allowing a more detailed study of the timing properties of the ABCD. The present results will be compared to a simulation of the charge collection and Front End electronics response.

The innermost layer (L00) of the Run IIa silicon detector of CDF was planned to be replaced for the high luminosity Tevatron upgrade of Run IIb. This new silicon layer (L0) is designed to be a radiation tolerant replacement for the otherwise very similar L00 from Run IIa. The data are read out via long, fine-pitch, low-mass cables allowing the hybrids with the chips to sit at higher z(/spl sim/70 cm), outside of the tracking volume. The design and first results from the prototyping phase are presented. Special focus is placed on the amount and the structure of induced noise as well as signal-to-noise values.

We describe the characteristics of silicon microstrip sensors fabricated by Hamamatsu Photonics for the CDF Run 2b silicon detector. A total of 953 sensors, including 117 prototype sensors, have been produced and tested. Five sensors were irradiated with neutrons up to 1.4 /spl times/10/sup 14/ n/cm/sup 2/ as a part of the sensor quality assurance program. The electrical and mechanical characteristics are found to be superior in all aspects and fulfill our specifications. We comment on charge-up susceptibility of the sensors that employ a <100> crystal structure.

The various generations of Silicon Vertex Detectors (SVX, SVX', SVXII) for Collider Detector at Fermilab (CDF) at the Fermilab Tevatron have been fundamental tools for heavy-flavor tagging via secondary vertex detection. The CDF Run IIb Silicon Vertex Detector (SVXIIb) has been designed to be a radiation-tolerant replacement for the currently installed SVXII because SVXII was not expected to survive the Tevatron luminosity anticipated for Run IIb. One major change in the new design is the use of a single mechanical and electrical element throughout the array. This element, called a stave, carries six single-sided silicon sensors on each side and is built using carbon fiber skins with a high thermal conductivity on a foam core with a built-in cooling channel. A Kapton bus cable carries power, data and control signals underneath the silicon sensors on each side of the stave. Sensors are read out in pairs via a ceramic hybrid glued on one of the sensors and equipped with four SVX4 readout chips. This new design concept leads to a very compact mechanical and electrical unit, allowing streamlined production and ease of testing and installation. A description of the design and mechanical performance of the stave is given. Results on the electrical performance obtained using prototype staves are also presented.

The main building block and readout unit of the planned CDF Run IIb silicon detector is a "stave," a highly integrated mechanical, thermal, and electrical structure. One of its characteristic features is a copper-on-Kapton flexible cable for power, high voltage, data transmission, and control signals that is placed directly below the silicon microstrip sensors. The dense packaging makes deadtime-less operation of the stave a challenge since coupling of bus cable activity into the silicon sensors must be suppressed efficiently. The stave design features relevant for deadtime-less operation are discussed. The electrical performance achieved with stave prototypes is presented.

This paper presents studies and measurements of the Lorentz angle and cluster size for the ATLAS Semiconductor Tracker (SCT). The performance of the SCT detector has been studied with cosmic rays d ...

Supersymmetric partners of charged leptons, scalar leptons were searched for in e+e− collisions at TRISTAN with center-of-mass energies up to 60.8 GeV. The pair production of unstable scalar leptons were searched for among identified lepton-pair events, and stable ones among collinear two-track events. No evidence was found for them. Mass limits are presented for both large-splitting and degenerate cases.

A search for sequential heavy leptons has been performed at the center-of-mass energy of 52 GeV at the KEK colliding-beam accelerator TRISTAN. We have found no evidence for the production of heavy leptons with the integrated luminosity of 2.9 ${\mathrm{pb}}^{\ensuremath{-}1}$. A lower mass limit of 25.0 GeV/${\mathit{c}}^{2}$ at 95% confidence level was obtained.

Excited electrons, e∗'s, have been searched for by making use of the processes e+e−→e+e−γγ and eγ(e) (quasi-real Compton scattering). From the former process, we have obtained the lower limit for the mass of e∗', 27.9 GeV/c. A good agreement with QED is observed in the latter process, and new upper limits have been set for the coupling strength λ as a function of the mass of e∗.

Using 773 muons found in hadronic events from 142 ${\mathrm{pb}}^{\ensuremath{-}1}$ of data at a c.m. energy of 57.8 GeV, we extract the cross section and forward-backward charge asymmetry for the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}b\overline{b}$ process, and the heavy quark fragmentation function parameters for the Peterson model. For the analysis of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}b\overline{b}$ process, we use a method in which the behavior of the $c$ quark and lighter quarks is assumed, with only that of the $b$ quark left indeterminate. The cross section and asymmetry for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}b\overline{b}$ are found to be ${R}_{b} = 0.57 \ifmmode\pm\else\textpm\fi{} 0.06(\mathrm{stat}) \ifmmode\pm\else\textpm\fi{} 0.08(\mathrm{syst})$ and ${A}_{b} = \ensuremath{-}0.59 \ifmmode\pm\else\textpm\fi{} 0.09 \ifmmode\pm\else\textpm\fi{} 0.09$, respectively. They are consistent with the standard model predictions. For the study of the fragmentation function we use the variable $〈{x}_{E}〉$, the fraction of the beam energy carried by the heavy hadrons. We obtain ${〈{x}_{E}〉}_{c}={0.56}_{\ensuremath{-}0.05\ensuremath{-}0.03}^{+0.04+0.03}$ and ${〈{x}_{E}〉}_{b}={0.65}_{\ensuremath{-}0.04\ensuremath{-}0.06}^{+0.06+0.05}$, respectively. These are in good agreement with previously measured values.

A possible contribution of neutral scalar bosons to the cross section of multihadron production at e + e - collisions was examined at center-of-mass energies between 55.0 and 60.8 GeV by taking into account first-order radiative corrections. We found no positive evidence and established new upper limits on the coupling parameter of the scalars.

The first beam-test results for two- and three-bundle shashlik tower prototypes are described. We found that the spatial resolution, the uniformity of energy response, the calorimeter reliability and hermeticity and also two showers separation are improved in multi-bundle design approach.

We have studied inclusive lepton production in e+e− annihilations into multihadrons in the energy range between √s=50 and 55 GeV using the VENUS detector at TRISTAN, KEK. Though MARK-J and JADE groups at PETRA found an excess of isolated muon events at √s⩾46.3 GeV, we have not observed such an anomaly in muon nor in electron production. The observed rates of isolated leptons are consistent with the production and decay of five known quarks.

Properties of proton diffractive dissociation have been investigated for four-prong final states in proton-proton reactions at 360 GeV/c, in particular forpp→ppπ +π− mπ 0(m=0,1,2). Mass distributions and decay angular distributions are given. The decay of the diffractive system is seen to be very anisotropic, and largep T is suppressed at higher masses. It is found that the “pomeron” couples with a single valence quark of the incident proton, but indications for a diquark-pomeron coupling are also found. Similarities with fragmentation in lepton-hadron deep inelastic scattering are underlined.

Abstract

We report on a measurement of the forward-backward charge asymmetry in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}$ at KEK TRISTAN, where the asymmetry is near maximum. We sum over all flavors and measure the asymmetry by determining the charge of the quark jets. In addition we exploit flavor dependencies in the jet charge determination to enhance the contributions of certain flavors. This provides a check on the asymmetries of individual flavors. The measurement agrees with the standard model expectations.

We evaluated pn-SiC (silicon carbide) particle detectors exposed to 5.486 MeV alpha particles from a sealed radioactive source of /sup 241/Am and 3.26 eV (380 nm) pulsed Ultra-Violet (UV) light at 100 Hz from a Light Emitting Diode (LED). The pn junction SiC diode was made by the implantation of phosphorus (P) ions (140, 60, 90 keV) into p-type 6H-SiC epitaxial layers (5 /spl mu/m) grown onto p/sup +/-type substrates. The mean pulse height from detector increased with the supplied reverse bias voltage for each irradiation, alpha particles and UV light. We discuss relation of the pulse height distribution obtained by the UV light and the alpha particles to the depletion width with diffusion length of carriers.

We report on measurements of the total cross section for e+e−→γγ for center-of-mass energies between 57.4 and 59.5 GeV, using the AMY detector at the TRISTAN collider. We set new limits on the production of a possible new s-channel resonance decaying into photon pairs.

Results of a search for the pair production of charged heavy leptons in e + e − annihilations over the center-of-mass energy range of 50 to 60.8 GeV are reported. We assume that the leptons are of the sequential type but have allowed for the case where the associated neutrino might be massive. Separate searches for evidence for decays to hadronic and leptonic final states, searches specialized for the case where the charged lepton and its associated neutrino are close in mass, and a search for stable heavy leptons have uncovered no evidence for the production of such particles at these energies. Mass limits for heavy leptons and their associated neutrinos are determined for a range of hadronic and leptonic decay branching fractions. A sequential charged heavy lepton with mass between 12.6 and 29.6 GeV/c 2 and with massless neutrino is excluded at the 95% confidence level.

A rack cooling system for the VENUS detector has been developed. It uses forced-air cooling and has enough cooling power for crates with as much as 1500 Watts of power consumption. The design and the cooling performance for FASTBUS crates are reported.

Shashlik calorimeter prototypes equipped with preshower detector have been tested in 3 T magnetic field with electron beam at CERN-SPS. The signal from electrons increases as much as 11% at 3 T magnetic field. No significant deterioration on the energy resolution as well as the preshower detector performance have been observed.

The ATLAS experiment is a general purpose experiment being constructed at the Large Hadron Collider (LHC) at CERN, Geneva. ATLAS is designed to exploit the full physics potential of LHC, in particular to study topics con- cerning the Higgs mechanism, Super-symmetry and CP violation. The cross sections for the processes under study are extremely small, requiring very high luminosity colliding beams. The SemiConductor Tracker (SCT) is an essential part of the Inner Detector tracking system of ATLAS. The active elements of the SCT is 4088 detector modules, tiled on four barrel cylinders and eighteen endcap disks. As a consequence of the high luminosity, the detector modules will operate in a harsh radiation environment. This the- sis describes work concerning radiation hardness, beam test performance and methods for production testing of detector modules. The radiation hardness studies have been focused on the electrical performance of the front-end ASIC and the detector module. The results have identifed features of the ASIC failing after irradiation and conrmed the good performance of the re-designed ASIC. The beam tests have been performed in the late prototyping and the pre-production phase, verifying the specied performance of the detector modules. Special effort have been made to evaluate the performance of irradiated detector modules. The assembly, quality assurance and characterisation of the detector modules will be done in the collaborating institutes. The thesis reports on methods developed for use during the production, to assess the electrical performance.

The present experimental tests of the electroweak universality in the leptonic sector are reviewed for both charged- and neutral-current electroweak interactions. To cite this article: A. Rougé, R. Tanaka, C. R. Physique 3 (2002) 1165–1172. Nous présentons l'état actuel des tests de l'universalité des interactions électrofaibles de type courant chargé et de type courant neutre dans le domaine des leptons. Pour citer cet article : A. Rougé, R. Tanaka, C. R. Physique 3 (2002) 1165–1172.

A novel hybrid structure for the barrel module of the ATLAS Semiconductor Tracker (SCT) is developed. The hybrid carries 12 bare readout chips totaling 1536 channels. A flexible copper-polyimide 4-layer lamination is used as a basic circuit. The circuit is re-enforced by two carbon-carbon bridges coated with Parylene polymer. The hybrid staffed by resistors, capacitors and pitch adaptors undergoes heat cycling and quality inspections. The hybrid after chip mounting and wire bonding is placed over the top and bottom sides of the module assembly with no direct contact to silicon sensors. Some twenty full-fledge modules with active silicon strip sensors were assembled Their electrical, mechanical as well as thermal performances of the module are proven to be excellent.