10064566
Study of Various Photomultiplier Tubes with Muon Beams And Cerenkov Light Produced in Electron Showers
The PMTs of the CMS Hadron Forward calorimeter were found to generate a large size signal when their windows were traversed by energetic charged particles. This signal, which is due to. Cerenkov light production at the PMT window, could interfere with the calorimeter signal and mislead the measurements. In order to find a viable solution to this problem, the response of four different types of PMTs to muons traversing their windows at different orientations is measured at the H2 beam-line at CERN. Certain kinds of PMTs with thinner windows show significantly lower response to direct muon incidence. For the four anode PMT, a simple and powerful algorithm to identify such events and recover the PMT signal using the signals of the quadrants without window hits is also presented. For the measurement of PMT responses to. Cerenkov light, the Hadron Forward calorimeter signal was mimicked by two different setups in electron beams and the PMT performances were compared with each other. Superior performance of particular PMTs was observed.
119232894
Search for heavy quarks decaying into a top quark and a W or Z boson using lepton + jets events in pp collisions at $ \sqrt{s}=7 $ TeV
A bstractResults are presented from a search for the pair-production of heavy quarks, $ \mathrm{Q}\overline{\mathrm{Q}} $, that decay exclusively into a top quark and a W or Z boson. The search is performed using a sample of proton-proton collisions at $ \sqrt{s}=7 $ TeV corresponding to an integrated luminosity of 5.0 fb−1, collected by the Compact Muon Solenoid experiment. The signal region is defined using a sample of events containing one electron or muon, missing transverse momentum, and at least four jets with large transverse momenta, where one jet is likely to originate from the decay of a bottom quark. No significant excess of events is observed with respect to the standard model expectations. Assuming a strong pair-production mechanism, quark masses below 675 (625) GeV decaying into tW (tZ) are excluded at the 95 % confidence level.
119163191
Search for a fermiophobic Higgs boson in pp collisions at $ \sqrt {s} = 7 $ TeV
A bstractCombined results are reported from searches for a fermiophobic Higgs boson in the γγ, WW, and ZZ decay modes in proton-proton collisions at $ \sqrt {s} = 7 $ TeV. The explored Higgs boson mass range is 110–300 GeV. The data sample corresponds to an integrated luminosity of 4.9–5.1 fb−1. A fermiophobic Higgs boson is excluded at 95% confidence level in the mass range 110–194 GeV, and at 99% confidence level in the mass ranges 110–124.5 GeV, 127–147.5 GeV, and 155–180 GeV.
209048432
Search for supersymmetry in hadronic final states with missing transverse energy using the variables alphaT and b-quark multiplicity in pp collisions at sqrt(s) = 8 TeV
118218838
Search for large extra dimensions in the diphoton final state at the Large Hadron Collider
A search for large extra spatial dimensions via virtual-graviton exchange in the diphoton channel has been carried out with the CMS detector at the LHC. No excess of events above the standard model expectations is found using a data sample collected in proton-proton collisions at $ \sqrt {s} = 7 $ TeV and corresponding to an integrated luminosity of 36 pb−1. New lower limits on the effective Planck scale in the range of 1.6–2.3TeV at the 95% confidence level are set, providing the most restrictive bounds to date on models with more than two large extra dimensions.
125583262
Scintillating fiber detectors using position sensitive photomultipliers
28803633
Measurement of the Cross Section for High-$p_T$ Hadron Production in Scattering of 160 GeV/c Muons off Nucleons
The cross section for production of charged hadrons with high transversemomenta in scattering of 160 GeV/c muons off nucleons at low photonvirtualities has been measured at the COMPASS experiment at CERN. The results,which cover transverse momenta from 1.1 to 3.6 GeV/c, are compared to anext-to-leading order perturbative Quantum Chromodynamics (NLO pQCD)calculation in order to evaluate the applicability of pQCD to this process inthe kinematic domain of the experiment. The shape of the calculateddifferential cross section as a function of transverse momentum is found to bein good agreement with the experimental data, but the normalization isunderestimated by NLO pQCD. This discrepancy may point towards the relevance ofterms beyond NLO in the pQCD framework. The dependence of the cross section onthe pseudo-rapidity and on the charge of the hadrons is also discussed.
55044418
Transverse spin effects in hadron-pair production from semi-inclusive deep inelastic scattering
First measurements of azimuthal asymmetries in hadron-pair production in deep-inelastic scattering of muons on transversely polarised LiD 6 (deuteron) and NH 3 (proton) targets are presented. The data were taken in the years 2002–2004 and 2007 with the COMPASS spectrometer using a muon beam of 160 GeV/ c at the CERN SPS. The asymmetries provide access to the transversity distribution functions, without involving the Collins effect as in single hadron production. The sizeable asymmetries measured on the NH 3 target indicate non-vanishing u -quark transversity and two-hadron interference fragmentation functions. The small asymmetries measured on the LiD 6 target can be interpreted as indication for a cancellation of u - and d -quark transversities.
18225120
Serendipitous Detections of XTE J1906+09 with the Rossi X-ray Timing Explorer
In 1996 during Rossi X-Ray Timing Explorer (RXTE) observations of SGR 1900+14, the 89 s X-ray pulsar XTE J1906+09 was discovered. As a result of monitoring campaigns of SGR 1900+14, XTE J1906+09 was also monitored regularly in 1996 September, 1998 May-June, 1998 August-1999 July, and 2000 March-2001 January. A search for pulsations in these observations resulted in detections of only the two previously reported outbursts in 1996 September and 1998 August-September. Pulsed flux upper limits for the remaining observations indicate that XTE J1906+09 is a transient X-ray pulsar and therefore likely has a Be star companion. XTE J1906+09 was not detected with the RXTE all-sky monitor. Pulse-timing analysis of the second outburst revealed a sinusoidal signature in the pulse frequencies that is likely produced by periastron passage in an orbit. Fits to pulse phases using an orbital model and quadratic phase model have χ2 minima at orbital periods of 26-30 days for fixed mass functions of 5, 10, 15, and 20 M☉. The pulse shape showed intensity- and energy-dependent variations. Pulse-phase spectroscopy was used to quantify the energy-dependent variations. The phase-averaged spectrum, using the pulse minimum spectrum as the background spectrum to eliminate effects from SGR 1900+14 and the Galactic ridge, was well fitted by an absorbed power law with a high-energy cutoff with column density NH = (6 ± 1) × 1022 cm-2, a photon index of 1.01 ± 0.08, cutoff energy Ecut = 11 ± 1 keV, and e-folding energy Efold = 19 ± 4 keV. Estimated 2-10 keV peak fluxes, corrected for contributions from the Galactic ridge and SGR 1900+14, are 6 × 10-12 and 1.1 × 10-10 ergs cm-2 s-1 for the 1996 and 1998 outbursts, respectively. XTE J1906+09 may be a member of an unusual class of Be/X-ray binaries that do not lie on the general spin period versus orbital period correlation with the majority of Be/X-ray binaries.
19155671
When A Standard Candle Flickers
The Crab Nebula is the only hard X-ray source in the sky that is both bright enough and steady enough to be easily used as a standard candle. As a result, it has been used as a normalization standard by most X-ray/gamma-ray telescopes. Although small-scale variations in the nebula are well known, since the start of science operations of the Fermi Gamma-ray Burst Monitor (GBM) in 2008 August, a ~7% (70 mCrab) decline has been observed in the overall Crab Nebula flux in the 15-50 keV band, measured with the Earth occultation technique. This decline is independently confirmed in the ~15-50 keV band with three other instruments: the Swift Burst Alert Telescope (Swift/BAT), the Rossi X-ray Timing Explorer Proportional Counter Array (RXTE/PCA), and the Imager on-Board the INTEGRAL Satellite (IBIS). A similar decline is also observed in the ~3-15 keV data from the RXTE/PCA and in the 50-100 keV band with GBM, Swift/BAT, and INTEGRAL/IBIS. The pulsed flux measured with RXTE/PCA since 1999 is consistent with the pulsar spin-down, indicating that the observed changes are nebular. Correlated variations in the Crab Nebula flux on a ~3 year timescale are also seen independently with the PCA, BAT, and IBIS from 2005 to 2008, with a flux minimum in 2007 April. As of 2010 August, the current flux has declined below the 2007 minimum.
59046605
UHECR Study on Satellites in TUS/KLYPVE Experi- ments
The TUS/KLYPVE space experiments have been proposed to study the energy spectrum, composition and arrival direction of the Ultra High Energy Cosmic Rays (UHECR) by detection from the space satellites of the atmosphere fluorescence and Cherenkov light produced by UHECR initiated Extensive Atmosphere Showers (EAS). The TUS set up is a prototype of the KLYPVE. The aim of the TUS experiment is to detect a dozen of UHECR events in the energy region of the GZK cutoff, to measure the light background, to test the atmosphere control methods, to study a stability of the optic materials, of PMTs, and of DAQ in the space environment.