143 research outputs found

    Timing Measurements in the Vertical Roman Pots of the TOTEM Experiment

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    The TOTEM upgrade programme focuses on improving the experiment’s capability to explore and measure new physics in Central Diffractive processes in two complementary projects, both based on the installation of proton-time-of-flight detectors in Roman Pots to reconstruct the longitudinal vertex position and thus to assign the proton vertex to the correct central CMS tracker vertex in the presence of event pileup. The present TDR discusses theinstrumentation developments, physics potential and performance for operation with a beta^* = 90 m beam optics, for which the vertical Roman Pots will be equipped with timing detectors with 50ps resolution. In this scenario, the leading proton acceptance covers all diffractive masses, provided that the protons’ four-momentum transfer |t| > 0.01 GeV^2. In a complementary way, the second project, the CMS-TOTEM Precision Proton Spectrometer(CT-PPS) for standard LHC fills at low b targeting processes with high diffractive masses (>300 GeV/c^2) and leading protons in the horizontal Roman Pots is described in another TDR

    First search for exclusive diphoton production at high mass with tagged protons in proton-proton collisions at √s = 13 TeV

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    A search for exclusive two-photon production via photon exchange in proton-proton collisions, p p → p γ γ p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb −1 collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons match the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% confidence level are | ζ 1 | < 2.9 × 10 −13     GeV −4 and | ζ 2 | < 6.0 × 10 −13     GeV −4

    CMS-TOTEM Precision Proton Spectrometer

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    This report describes the technical design and outlines the expected performance of the CMS-TOTEM Precision Proton Spectrometer (CT-PPS). CT-PPS adds precision proton tracking and timing detectors in the very forward region on both sides of CMS at about 200m from the IP to study central exclusive production (CEP) in proton-proton collisions. CEP provides a unique method to access a variety of physics topics at high luminosity LHC, such as new physics via anomalous production of W and Z boson pairs, high-pT jet production, and possibly the production of new resonances. The CT-PPS detector consists of a silicon tracking system to measure the position and direction of the protons, and a set of timing counters to measure their arrival time with a precision of the order of 10 ps. This in turn allows the reconstruction of the mass and momentum as well as of the z coordinate of the primary vertex of the centrally produced system. The framework for the development and exploitation of CT-PPS is defined in a Memorandum of Understanding signed by CERN as the host laboratory and the CMS and TOTEM Collaborations. The expected performance of CT-PPS is discussed, including detailed studies of exclusive WW and dijet production. The planning for the implementation of the new detectors is presented, including construction, testing, and installation

    Measurement of single-diffractive dijet production in proton–proton collisions at √s = 8 TeV with the CMS and TOTEM experiments

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    Measurements are presented of the singlediffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss ξ and the four-momentum transfer squared t. Both processes pp → pX and pp → Xp, i.e. with the proton scattering to either side of the interaction point, are measured, where X includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton–proton collisions at √ s = 8 TeV during a dedicated run with β ∗ = 90m at low instantaneous luminosity and correspond to an integrated luminosity of 37.5nb−1. The single-diffractive dijet cross section σ pX jj , in the kinematic region ξ 40 GeV, and pseudorapidity |η| < 4.4, is 21.7 ± 0.9 (stat) +3.0 −3.3 (syst) ± 0.9 (lumi) nb. The ratio of the single-diffractive to inclusive dijet yields, normalised per unit of ξ , is presented as a function of x, the longitudinal momentum fraction of the proton carried by the struck parton. The ratio in the kinematic region defined above, for x values in the range −2.9 ≤ log10 x ≤ −1.6, is R = (σ pX jj / ξ)/σjj = 0.025 ± 0.001 (stat) ± 0.003 (syst), where σ pX jj and σjj are the single-diffractive and inclusive dijet cross sections, respectively. The results are compared with predictions from models of diffractive and nondiffractive interactions. Monte Carlo predictions based on the HERA diffractive parton distribution functions agree well with the datawhen corrected for the effect of soft rescattering between the spectator partons

    Addendum to the TOTEM TDR : Timing Measurements in the Vertical Roman Pots of the TOTEM Experiment LHCC document CERN-LHCC-2014-020 including questions/answers from/to the referees

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    This document details the answer to the questions and observation raised by the referees after the LHCC open presentation of the TOTEM Timing Upgrade TDR

    Neutrino Beams From Electron Capture at High Gamma

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    We investigate the potential of a flavor pure high gamma electron capture electron neutrino beam directed towards a large water cherenkov detector with 500 kt fiducial mass. The energy of the neutrinos is reconstructed by the position measurement within the detector and superb energy resolution capabilities could be achieved. We estimate the requirements for such a scenario to be competitive to a neutrino/anti-neutrino running at a neutrino factory with less accurate energy resolution. Although the requirements turn out to be extreme, in principle such a scenario could achieve as good abilities to resolve correlations and degeneracies in the search for sin^2(2 theta_13) and delta_CP as a standard neutrino factory experiment.Comment: 21 pages, 7 figures, revised version, to appear in JHEP, Fig.7 extended, minnor changes, results unchange

    Measurement of pseudorapidity distributions of charged particles in proton–proton collisions at s√=8 TeV by the CMS and TOTEM experiments

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    This is the published version.Pseudorapidity (η) distributions of charged particles produced in proton–proton collisions at a centre-of-mass energy of 8 TeV are measured in the ranges |η|<2.2 and 5.3<|η|<6.4 covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of L=45 μb−1. Measurements are presented for three event categories. The most inclusive category is sensitive to 91–96 % of the total inelastic proton–proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single diffractive dissociation events. The data are compared to models used to describe high-energy hadronic interactions. None of the models considered provide a consistent description of the measured distributions

    Physics at the LHC: a short overview

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    The CERN Large Hadron Collider (LHC) started operation a few months ago. The machine will deliver proton-proton and nucleus-nucleus collisions at energies as high as sqrt(s)=14 TeV and luminosities up to L~10^{34} cm^{-2}s^{-1}, never reached before. The main open scientific questions that the seven LHC experiments -- ATLAS, CMS, ALICE, LHCb, TOTEM, LHCf and MOEDAL -- aim to solve in the coming years are succinctly reviewed.Comment: 9 pages, 16 plots. Invited review talk Hot-Quarks 2010, La Londe-Les-Maures, July 2010. J. Phys. Conf. Ser. 270, 012001 (2011). Minor typos correcte

    Forward production of beauty baryons in pp collisions at LHC

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    The production of charmed and beauty baryons in proton-proton collisions at high energies is analyzed within the modified quark-gluon string model. We present some predictions for the experiments on the forward beauty baryon production in pp collisions at LHC energies. This analysis allows us to find useful information on the Regge trajectories of the heavy (b barb) mesons and the sea beauty quark distributions in the proton.Comment: 14 pages, 12 figure