• on behalf of the CMS Collaboration

      Articles written in Pramana – Journal of Physics

    • Understanding the performance of CMS calorimeter

      Seema Sharma on behalf of the CMS Collaboration

      More Details Abstract Fulltext PDF

      The performance of the CMS hadron calorimeter is studied using test beam facilities at CERN. Two wedges of brass-scintillator calorimeter are exposed to negative and positive beams with momenta between 3 and 300 GeV/c. Light produced in the scintillators are collected using wavelength shifting fibres and read out using hybrid photo-diodes. Each of the wedges has 17 layers of scintillators. In one of these wedges signal from all 17 layers are grouped together while in the other each layer is read out separately. The response, energy resolution, longitudinal and lateral shower profiles are measured.

    • Data-driven performance evaluation method for CMS RPC trigger system using 2011 data at LHC

      A Sharma S B Beri on behalf of the CMS Collaboration

      More Details Abstract Fulltext PDF

      The compact muon solenoid (CMS) is one of the four experiments which is getting and analysing the results of the collision of protons at LHC. The CMS trigger system is divided into two stages, the level-1 trigger and high-level triggers, to handle the large stream of data produced in collision. The information transmitted from the three muon subsystems (DT, CSC and RPC) are collected by the Global Muon Trigger (GMT) Board and merged. A method for evaluating the RPC system trigger efficiency with data from $pp$ collision was developed using the features of GMT. The results of the study with the real data of 2011 are shown and discussed here along with the comparison of Monte Carlo results

    • Dijet physics with CMS detector at the Large Hadron Collider

      Suvadeep Bose on behalf of the CMS Collaboration

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      The results from various dijet distributions in proton-proton collisions at a centre-of-mass energy of 7 TeV, with 2010 and 2011 data from the CMS experiment, are presented. The measurements of the dijet mass spectra, centrality ratio, azimuthal decorrelation and angular distribution are shown. Sensitivity of the phenomenological parameters used to model different event generators is also investigated. Prospects for observing evidence for new physics in these distributions are presented.

    • Search for the Standard Model Higgs boson produced in the decay channel $H \rightarrow ZZ \rightarrow 2l2\tau$ with CMS detector at $\sqrt{s} = 7$ TeV

      Chhibra Simranjit Singh on behalf of the CMS Collaboration

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      Search for the Standard Model Higgs boson in the decay mode $H \rightarrow ZZ \rightarrow 2l2\tau$, where $l = \mu, e$, is presented based on CMS data corresponding to an integrated luminosity of 1.1 fb-1 at $\sqrt{s} = 7$ TeV. No evidence is found for a significant deviation from Standard Model expectations anywhere in the $ZZ$ mass range considered in this analysis. An upper limit at 95% CL is placed on the product of the cross-section and decay branching ratio for the Higgs boson decaying with Standard Model-like couplings, which excludes cross-sections of about ten times the expected value for Higgs boson masses in the range 200 < $m_{H}$< 400 GeV/c2.

    • Search for heavy resonances decaying to tau pairs with the CMS detector at the Large Hadron Collider

      N Dhingra on behalf of the CMS Collaboration

      More Details Abstract Fulltext PDF

      A search for heavy resonance production decaying to tau pair is performed in the proton–proton collisions at the center-of-mass energy $\sqrt{s} = 7$ TeV using 36 pb-1 of data collected with CMS detector at the LHC during the year 2010. The number of observed events are in good agreement with the predictions of Standard Model background processes. Therefore, an upper limit on the resonance cross-section times the branching ratio to tau pair is obtained as a function of the resonance mass. Ditau resonance Z' with Standard Model couplings having mass less than 468 GeV/c2 is excluded at 95% confidence level.

    • Search for excited leptons in pp collisions at $\sqrt{s} = 7$ TeV

      Shilpi Jain on behalf of the CMS Collaboration

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      A search for excited leptons, carried out with the CMS detector in $pp$ collision at the LHC with $\sqrt{s} = 7$ TeV, is presented. The search has been performed for an associated production of a lepton and an oppositely charged excited lepton $pp \rightarrow ll^{*}$, followed by the decay $l^{*} \rightarrow l\gamma$ , resulting in $ll\gamma$ final state, where $l = e,\mu$. No excess above the Standard Model expectation is observed in the data. Interpreting the findings in the context of $l^{∗}$ production through four-fermion contact interactions and $l^{∗}$ decay via electroweak processes, upper limits are reported for $l^{∗}$ production at this collision energy and the exclusion region in the $\Lambda - M(l^{*})$ parameter space is extended beyond the previously established limits.

    • Measurement of the Drell–Yan differential cross-section $d\sigma/dM$ at $\sqrt{s} = 7$ TeV

      M Jindal on behalf of the CMS Collaboration

      More Details Abstract Fulltext PDF

      The Drell–Yan differential cross-section is measured in proton–proton collisions at $\sqrt{s} = 7$ TeV, from a data sample collected with the CMS detector at the LHC and corresponding to an integrated luminosity of $36 \pm 1.4$ pb-1. The measured cross-section is normalized to the cross-section of the 𝑍-peak region, for both dimuon and dielectron final state, in the dilepton invariant mass range of 15–600 GeV/c2. The normalized cross-section values are quoted in the full phase-space and within the detector acceptance. The effect of final-state radiation is also studied and the measurements are correted for this. The measurements are compared to the theoretical predictions and are found to be in good agreement.

    • Measurement of single top production in $pp$ collisions at 7 TeV with the CMS detector

      Jyothsna Rani Komaragiri on behalf of the CMS Collaboration

      More Details Abstract Fulltext PDF

      The measurement of 𝑡-channel single top cross-section in proton–proton collisions at the Large Hadron Collider (LHC) at a centre-of-mass energy of 7 TeV, using data collected with the Compact Muon Solenoid (CMS) experiment during the year 2010 is presented. Both the electronneutrino and muon-neutrino decay channels of 𝑊 boson from top decay are considered. Two complementary multivariate analysis methods to separate signal and background and to extract the cross-section for the single top produced in 𝑡-channel are explored. The result is compared with the most precise Standard Model theory predictions.

    • Search for the Higgs boson in $H \rightarrow W W \rightarrow 2l2\nu$ mode with the CMS detector

      N Nishu S B Beri on behalf of the CMS Collaboration

      More Details Abstract Fulltext PDF

      A search is reported for the Higgs boson decaying to $W^{+} W^{−}$ in pp collisions at $\sqrt{s} = 7$ TeV. The analysis is performed using LHC data recorded by the CMS detector, corresponding to an integrated luminosity of 1.55 fb-1. No significant excess above the Standard Model background expectation is observed, and upper limits on Higgs boson production are derived, excluding the presence of a Higgs boson with a mass in the range of 147–194 GeV/c2 at the 95% confidence level (CL) using the CLs approach.

    • $W/Z +$jet(s) production in pp collisions at $\sqrt{s} = 7$ TeV

      S B Beri L K Saini A P Singh on behalf of the CMS Collaboration

      More Details Abstract Fulltext PDF

      The measurements of the cross-sections are presented for the production of jets in association with 𝑊 and 𝑍 bosons reconstructed in their decays to electrons and muons. The results are based on 36 pb-1 of $pp$ collisions at $\sqrt{s} = 7$ TeV collected by the CMS Collaboration. Jets are reconstructed with the CMS particle flow algorithm and must pass a transverse momentum threshold of 30 GeV. The study presents the ratios $\sigma (V + \geq n-{\text{jet}})/\sigma (V)$ and $\sigma (V + \geq n-{\text{jet}})/\sigma(V + \geq (n - 1)-{\text{jet}}).$ The comparison between the data and the Monte Carlo prediction is also showed.

    • Search for the Standard Model Higgs boson in the decay channel $H \rightarrow ZZ^{(∗)} \rightarrow 4l$ at CMS

      Chahal Gurpreet Singh on behalf of the CMS Collaboration

      More Details Abstract Fulltext PDF

      A search for the Standard Model (SM) Higgs boson in the decay channel $H \rightarrow ZZ^{(∗)} \rightarrow 4l$ with each 𝑍 boson decaying to an electron or muon pair is presented using $pp$ collisions from the LHC at $\sqrt{s} = 7$ TeV. The data analysed correspond to an integrated luminosity of $1.66 \pm 0.07$ fb-1 recorded by the CMS detector in 2010 and 2011. The search covers Higgs boson mass $(m_{\text{H}})$ hypotheses of $110 < m_{\text{H}} < 600$ GeV/c2. Twenty-one events are observed, while $21.2 \pm 0.8$ events are expected from Standard Model (SM) background processes. The events are not clustered in mass excluding interpretation as the SM Higgs boson and its $(4l)$ mass distribution is consistent with the expectation of SM continuum production of $ZZ^{(∗)}$ pairs. Upper limits at 95% CL on the cross-section × branching ratio for a SM Higgs boson with SM like decays exclude cross-sections from about once to twice the expected SM cross-section for masses in the range of $150 < m_{\text{H}}< 420$ GeV/c2.

    • Search for a Higgs boson decaying into two photons in the CMS detector

      Roberta Volpe on behalf of the CMS Collaboration

      More Details Abstract Fulltext PDF

      A search for a Higgs boson decaying into two photons in $pp$ collisions at the LHC at a centre-of-mass energy of 7 TeV is presented. The analysis is performed on a dataset corresponding to 1.66 fb-1 of data recorded in 2011 by the CMS experiment. Limits are set on the cross-section of a Standard Model Higgs boson decaying into two photons, and on the cross-section of a fermiophobic Higgs boson decaying into two photons.

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