Study of leptoquark pair production at the LHC with the CMS detector

We study the discovery potential of the CMS detector for the scalar leptoquark pair production at the LHC. Present and future exclusion limits are considered. We find that the maximal leptoquark mass reach is about 1.47 TeV for the branching ratio of Br(LQ_l -> l q)=100 %, while for Br(LQ_l -> l q)=50 % the upper limit is 1.2 TeV for an integrated luminosity of 100 fb-1. We obtain comparable results for electron and muon-type leptoquarks. The pileup effect at high luminosity is discussed.Comment: 10 pages, 7 figures, 4 tables, UNIX LaTe

Calorimetry Task Force Report

In this note we summarize the studies and recommendations of the calorimeter simulation task force (CaloTF). The CaloTF was established in February 2008 in order to understand and reconcile the discrepancies observed between the CMS calorimetry simulation and the test beam data recorded during 2004 and 2006. As the result of studies by the CaloTF a new version of Geant4 was developed and introduced in the CMS detector simulation leading to significanly better agreement with test beam data. Fast and flexible parameterizations describing showering in the calorimeter are introduced both in the Full Simulation (with a Gflash-like approach) and in the Fast Simulation. The CaloTF has developed a strategy to rapidly tune the CMS calorimeter simulation using the first LHC collision data when it becomes available. The improvements delivered by the CaloTF have been implemented in the software release CMSSW 2.1.0

Simultaneous Search for Two Higgs Bosons of Minimal Supersymmetry at the LHC

The prospects of detecting the CP-odd Higgs pseudoscalar ($A$) in the minimal supersymmetric model via its decay into a $Z$ boson and the lighter CP-even Higgs scalar ($h$) at the CERN Large Hadron Collider are investigated. The final state of $Z \to l^+l^-$ and $h \to b\bar{b}$, may provide a promising way to simultaneously detect the $A$ and the $h$. The compact muon solenoid detector performance is adopted for a realistic study of observability. In this discovery channel, the masses of the $h$ and the $A$ can be reconstructed. The impact of supersymmetric decay modes is considered.Comment: 17 pages, REVTEX, 6 figure

Energy Response and Longitudinal Shower Profiles Measured in CMS HCAL and Comparison With Geant4

The response of the CMS combined electromagnetic and hadron calorimeter to beams of pions with momenta in the range 5-300 GeV/c has been measured in the H2 test beam at CERN. The raw response with the electromagnetic compartment calibrated to electrons and the hadron compartment calibrated to 300 GeV pions may be represented by sigma = (1.2) sqrt{E} oplus (0.095) E. The fraction of energy visible in the calorimeter ranges from 0.72 at 5 GeV to 0.95 at 300 GeV, indicating a substantial nonlinearity. The intrinsic electron to hadron ratios are fit as a function of energy and found to be in the range 1.3-2.7 for the electromagnetic compartment and 1.4-1.8 for the hadronic compartment. The fits are used to correct the non-linearity of the e pi response to 5% over the entire measured range resulting in a substantially improved resolution at low energy. Longitudinal shower profile have been measured in detail and compared to Geant4 models, LHEP-3.7 and QGSP-2.8. At energies below 30 GeV, the data, LHEP and QGSP are in agreement. Above 30 GeV, LHEP gives a more accurate simulation of the longitudinal shower profile

Design, Performance, and Calibration of CMS Hadron Endcap Calorimeters

Detailed measurements have been made with the CMS hadron calorimeter endcaps (HE) in response to beams of muons, electrons, and pions. Readout of HE with custom electronics and hybrid photodiodes (HPDs) shows no change of performance compared to readout with commercial electronics and photomultipliers. When combined with lead-tungstenate crystals, an energy resolution of 8\% is achieved with 300 GeV/c pions. A laser calibration system is used to set the timing and monitor operation of the complete electronics chain. Data taken with radioactive sources in comparison with test beam pions provides an absolute initial calibration of HE to approximately 4\% to 5\%

Design, Performance and Calibration of the CMS Forward Calorimeter Wedges

We report on the test beam results and calibration methods using charged particles of the CMS Forward Calorimeter (HF). The HF calorimeter covers a large pseudorapidity region (3\l |\eta| \le 5), and is essential for 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. 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 \approx 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 a/\sqrt{E} + 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%

Design, Performance, and Calibration of the CMS Hadron-Outer Calorimeter

The CMS hadron calorimeter is a sampling calorimeter with brass absorber and plastic scintillator tiles with wavelength shifting fibres for carrying the light to the readout device. The barrel hadron calorimeter is complemented with an outer calorimeter to ensure high energy shower containment in the calorimeter. Fabrication, testing and calibration of the outer hadron calorimeter are carried out keeping in mind its importance in the energy measurement of jets in view of linearity and resolution. It will provide a net improvement in missing \et measurements at LHC energies. The outer hadron calorimeter will also be used for the muon trigger in coincidence with other muon chambers in CMS

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio