CMS pixel detector upgrade

Starting in 2013, the Large Hadron Collider (LHC) accelerator at CERN will deliver an increased luminosity, with an eventual goal of reaching 10(35) cm(-')(2)s(-')(1), to the Compact Muon Solenoid (CMS) experiment. This increase will happen in two steps creating far reaching implications for the CMS detector, especially for the tracking system. The first step, Phase I, will double the LHC luminosity and only the pixel tracker detector will be replaced. The second step, Phase II or SLHC, will requi re a new granularity of the strip detector which should substitute its strips with short strips or `strixels'. SLHC will also provide an unprecedented track rate and radiation level that demands a completely new readout architecture. This paper addresses these challenges, focusing on the replacement of the CMS inner pixel detector for Phase I and shows the status of the activities

Inclusive b-hadron production cross section with muons in pp collisions at s√=7TeV

A measurement of the b-hadron production cross section in proton-proton collisions at s√=7TeVs=7TeV is presented. The dataset, corresponding to 85 nb−1, was recorded with the CMS experiment at the LHC using a low-threshold single-muon trigger. Events are selected by the presence of a muon with transverse momentum pμT>6GeVpTμ>6GeV with respect to the beam direction and pseudorapidity |η μ | < 2.1. The transverse momentum of the muon with respect to the closest jet discriminates events containing b hadrons from background. The inclusive b-hadron production cross section is presented as a function of muon transverse momentum and pseudorapidity. The measured total cross section in the kinematic acceptance is σ(pp → b + X → μ + X′) = 1.32 ± 0.01(stat) ± 0.30(syst) ± 0.15(lumi)μb

Search for Dijet Resonances in 7 TeV pp Collisions at CMS

This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.211801.A search for narrow resonances in the dijet mass spectrum is performed using data corresponding to an integrated luminosity of 2.9  pb(−1) collected by the CMS experiment at the Large Hadron Collider. Upper limits at the 95% confidence level are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark-quark, quark-gluon, or gluon-gluon pairs. The data exclude new particles predicted in the following models at the 95% confidence level: string resonances, with mass less than 2.50 TeV, excited quarks, with mass less than 1.58 TeV, and axigluons, colorons, and E6 diquarks, in specific mass intervals. This extends previously published limits on these models

Observation of long-range, near-side angular correlations in proton-proton collisions at the LHC

This is the publisher's version, also available electronically from http://link.springer.com/article/10.1007%2FJHEP09%282010%29091.Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (η) and azimuthal angle (ϕ). Short-range correlations in Δη, which are studied in minimum bias events, are characterized using a simple “independent cluster” parametrization in order to quantify their strength (cluster size) and their extent in η (cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb(−1) data set at 7 TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate p T of 1–3 GeV/c, 2.0 < |Δη| < 4.8 and Δϕ ≈ 0. This is the first observation of such a long-range, near-side feature in two-particle correlation functions in pp or pp-bar collisions

Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at s√=0.9 and 2.36 TeV

This is the publisher's version, also available electronically from http://link.springer.com/article/10.1007%2FJHEP02%282010%29041.Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at s√=0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between --2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN (ch)/dη|(|η|)<0.5, are 3:48 ± 0:02 (stat.) ± 0.13 (syst.) and 4:47 ± 0:04 (stat.) ± 0.16 (syst.), respectively. The results at 0.9 TeV are in agreement with previous measurements and confirm the expectation of near equal hadron production in p-bar p and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date

The 2003 Tracker Inner Barrel Beam Test

Before starting the CMS Silicon Strip Tracker (SST) mass production, where the quality control tests can only be done on single components, an extensive collection of activities aiming at validating the tracker system functionality has been performed. In this framework, a final component prototype of the Inner Barrel part (TIB) of the SST has been assembled and tested in the INFN laboratories and then moved to CERN to check its behaviour in a 25~ns LHC-like particle beam. A set of preproduction single-sided silicon microstrip modules was mounted on a mechanical structure very similar to a sector of the third layer of the TIB and read out using a system functionally identical to the final one. In this note the system setup configuration is fully described and the results of the test, concerning both detector performance and system characteristics, are presented and discussed

Assembly of the Inner Tracker Silicon Microstrip Modules

This note describes the organization of the mechanical assembly of the nearly 4000 silicon microstrip modules that were constructed in Italy for the Inner Tracker of the CMS experiment. The customization and the calibration of the robotic system adopted by the CMS Tracker community, starting from a general pilot project realized at CERN, is described. The step-by-step assembly procedure is illustrated in detail. Finally, the results for the mechanical precision of all assembled modules are reported

Study of radiation damage and substrate resistivity effects from beam test of silicon microstrip detectors using LHC readout electronics

We present the beam test results of single-sided silicon microstrip detectors, with different substrate resistivities. The effects of radiation damage are studied for a detector irradiated to a fluence of 2.4 multiplied by 10**1**4 n/cm**2. The detectors are read out with the APV6 chip, which is compatible with the 40 MHz LHC clock. The performance of different detectors and readout modes are studied in terms of signal-to-noise ratio and efficiency