144 research outputs found
Exotic Physics Searches at CMS
No full textWe summarize the results of several searches for evidence of new physics phenomena using proton-proton collisions at √s = 7 TeV delivered by the Large Hadron Collider at CERN and recorded by the CMS detector in 2011
Studies of the Z\rightarrow ee differential cross section as a function of the Z rapidity in CMS
No full textRecommended from our members
A Study of Factorization and a Measurement of CP Violation
No full textWe report on a study of the decay {bar B}{sup 0} {yields} D*{sup +} {omega}{pi}{sup -} with the BABAR detector at the PEP-II B-factory at the Stanford Linear Accelerator Center. Based on a sample of 232 million B{sup 0}{bar B}{sup 0} decays collected between 1999 and 2004, we measure the branching fraction {Beta}({bar B}{sup 0} {yields} D*{sup +} {omega}{pi}{sup -}) = (2.88 {+-} 0.21(stat.) {+-} 0.31(syst.)) x 10{sup -3}. We study the invariant mass spectrum of the {omega}{pi}{sup -} system in this decay. This spectrum is in good agreement with expectations based on factorization and the measured spectrum in {tau}{sup -} {yields} {omega}{pi}{sup -} {nu}{sub {tau}}. We also measure the polarization of the D*{sup +} as a function of the {omega}{pi}{sup -} mass. In the mass region 1.1 to 1.9 GeV we measure the fraction of longitudinal polarization of the D*{sup +} to be {Lambda}{sub L}/{Lambda} = 0.654 {+-} 0.042(stat.) {+-} 0.016(syst.). This is in agreement with the expectations from heavy-quark effective theory and factorization assuming that the decay proceeds as {bar B}{sup 0} {yields} D*{sup +} {rho}(1450){sup -}, {rho}(1450){sup -} {yields} {omega}{pi}{sup -}. Furthermore, we present the results on the time-dependent CP asymmetry in neutral B meson decays to the CP eigenstate J/{psi}K{sub L}. The measurements use a data sample of about 88 million {Upsilon}(4S) {yields} B{bar B} decays collected between 1999 and 2002 with the BABAR detector. We study events in which one neutral B meson is fully reconstructed in the J/{psi}K{sub L} final state and the other B meson is determined to be either a B{sup 0} or a {bar B}{sup 0} from its decay products. The amplitude of the CP asymmetry, which in the Standard Model is proportional to sin 2{beta}, is derived from the decay-time distributions in such events. We measure sin 2{beta} = 0.723 {+-} 0.158(stat.) {+-} 0.086(syst.), which is consistent with Standard Model expectations
A Proposal to Increase the L1 Trigger Efficiency of Z-boson Detection in the CMS detector at the Large Hadron Collider
No full texti Acknowledgments This work could not have been completed without the assistance of the high-energy research group at the University of Minnesota. Specifically, the contributions of the following people were indispensable: graduate students Alex Gude, and Kevin Klapoetke; postdoctoral research associate Bryan Dahmes, and, of course, Professor Jeremy Mans, who provided essential guidance throughout the project. Solenoid experiment is expected to be overwhelmed by projected luminosity increases at the Large Hadron Collider. The ensuing necessary prescaling of data would negatively impact Zdecay physics. It is proposed to implement a new trigger bit which utilizes leading HF rank to more efficiently identify di-lepton ECAL-HF Z-decay events. To establish the feasibility of this option, data containing known examples of these events is compared to the subset of background data where the L1 Single EG12 bit had fired. It is shown that the leading HF jet ranks of desired 'signal' events are significantly higher than those of 'background events, suggesting inclusion of leading HF rank in triggering criteria. The proposed trigger bit would eliminate all events with a leading HF rank less than four, corresponding to less than 16 GeV of transverse energy in HF. This would reduce the triggering rate by a factor of 6.08 while still preserving 99.9 percent of signal events, rendering a prescale of di-lepton Z-decay data unneccesary
Commissioning of the CMS High Level Trigger
No full textThe CMS experiment will collect data from the proton-proton collisions delivered by the Large Hadron Collider (LHC) at a centre-of-mass energy up to 14 TeV. The CMS trigger system is designed to cope with unprecedented luminosities and LHC bunch-crossing rates up to 40 MHz. The unique CMS trigger architecture only employs two trigger levels. The Level-1 trigger is implemented using custom electronics, while the High Level Trigger (HLT) is based on software algorithms running on a large cluster of commercial processors, the Event Filter Farm. We present the major functionalities of the CMS High Level Trigger system as of the starting of LHC beams operations in September 2008. The validation of the HLT system in the online environment with Monte Carlo simulated data and its commissioning during cosmic rays data taking campaigns are discussed in detail. We conclude with the description of the HLT operations with the first circulating LHC beams before the incident occurred the 19th September 2008.The CMS experiment will collect data from the proton-proton collisions delivered by the Large Hadron Collider (LHC) at a centre-of-mass energy up to 14 TeV. The CMS trigger system is designed to cope with unprecedented luminosities and LHC bunch-crossing rates up to 40 MHz. The unique CMS trigger architecture only employs two trigger levels. The Level-1 trigger is implemented using custom electronics, while the High Level Trigger (HLT) is based on software algorithms running on a large cluster of commercial processors, the Event Filter Farm. We present the major functionalities of the CMS High Level Trigger system as of the starting of LHC beams operations in September 2008. The validation of the HLT system in the online environment with Monte Carlo simulated data and its commissioning during cosmic rays data taking campaigns are discussed in detail. We conclude with the description of the HLT operations with the first circulating LHC beams before the incident occurred the 19th September 2008
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