5,412 research outputs found

### Measurement of the inelastic proton-proton cross section at $\sqrt{s}$ = 13 TeV

A measurement of the inelastic proton-proton cross section at a
centre-of-mass energy of $\sqrt{s}$ = 13 TeV is presented. The analysis is
performed using the CMS detector, in particular with information from forward
calorimetry at pseudorapidities of 3.0 < {\eta} < 5.2 and -6.6 < {\eta} < -3.0.
A visible cross section is measured in two different detector acceptances and
finally extrapolated to the full inelastic phase space domain. The results are
compared with those of other experiments, and with models used to describe
high-energy hadronic interactions.Comment: 5 pages, 2 figures, proceedings of the XXIV International Workshop on
Deep-Inelastic Scattering and Related Subjects, 11-15 April 2016, DESY
Hamburg, German

### Treating jet correlations in high pile-up at hadron colliders

Experiments in the high-luminosity runs at the Large Hadron Collider face the
challenges of very large pile-up. Primary techniques to deal with this are
based on precise vertex and track reconstruction. Outside tracker acceptances,
however, lie regions of interest for many aspects of the LHC physics program.
We explore complementary approaches to pile-up treatment and propose a
data-driven jet-mixing method which can be used outside tracker acceptances
without depending on Monte Carlo generators. The method can be applied to treat
correlation observables and take into account, besides the jet transverse
momentum pedestal, effects of hard jets from pile-up.Comment: Latex. 8 pages, 5 figure

### Measurements of the forward energy flow and forward jet production with CMS

We present measurements of the forward (3 < |eta| < 5) energy flow in minimum
bias events and in events with either hard jets or W and Z bosons produced at
central rapidities together with first measurements of the inclusive forward
jet cross section and central forward jet correlations. Results are compared to
MC models with different parameter tunes for the description of the underlying
event.Comment: 8 pages, DPF 2011 conference proceeding

### Higgs boson as a gluon trigger: the study of QCD in high pile-up environments

In the forthcoming high-luminosity phase of the LHC many of the most
interesting measurements for precision QCD studies are hampered by large
pile-up conditions, especially at not very high transverse momenta. However,
with the recently discovered Higgs boson, which couples in the heavy top limit
directly to gluons, we have access to a novel production process to probe QCD
by a colour-singlet current. In this study we compare observables in Higgs
boson and Drell-Yan production and investigate whether measuring ratios or
subtractions can yield results that are stable in high pile-up environments,
and yet sensitive to (small-$p_{\text{T}}$) QCD physics in gluon fusion
processes. We present results of Monte Carlo event generator calculations for a
few specific examples.Comment: 7 pages, 10 figures, DIS2014 conference proceeding

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### Measurement of double-differential cross sections for top quark pair production in pp collisions at [Formula: see text][Formula: see text] and impact on parton distribution functions.

Normalized double-differential cross sections for top quark pair ([Formula: see text]) production are measured in pp collisions at a centre-of-mass energy of 8[Formula: see text] with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7[Formula: see text]. The measurement is performed in the dilepton [Formula: see text] final state. The [Formula: see text] cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and [Formula: see text] system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured [Formula: see text] cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution

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### A search for new phenomena in pp collisions at [Formula: see text] in final states with missing transverse momentum and at least one jet using the [Formula: see text] variable.

A search for new phenomena is performed in final states containing one or more jets and an imbalance in transverse momentum in pp collisions at a centre-of-mass energy of 13[Formula: see text]. The analysed data sample, recorded with the CMS detector at the CERN LHC, corresponds to an integrated luminosity of 2.3[Formula: see text]. Several kinematic variables are employed to suppress the dominant background, multijet production, as well as to discriminate between other standard model and new physics processes. The search provides sensitivity to a broad range of new-physics models that yield a stable weakly interacting massive particle. The number of observed candidate events is found to agree with the expected contributions from standard model processes, and the result is interpreted in the mass parameter space of fourteen simplified supersymmetric models that assume the pair production of gluinos or squarks and a range of decay modes. For models that assume gluino pair production, masses up to 1575 and 975[Formula: see text] are excluded for gluinos and neutralinos, respectively. For models involving the pair production of top squarks and compressed mass spectra, top squark masses up to 400[Formula: see text] are excluded

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### Measurement of the [Formula: see text] production cross section using events in the [Formula: see text] final state in pp collisions at [Formula: see text].

The cross section of top quark-antiquark pair production in proton-proton collisions at [Formula: see text] is measured by the CMS experiment at the LHC, using data corresponding to an integrated luminosity of 2.2[Formula: see text]. The measurement is performed by analyzing events in which the final state includes one electron, one muon, and two or more jets, at least one of which is identified as originating from hadronization of a b quark. The measured cross section is [Formula: see text], in agreement with the expectation from the standard model

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### Measurement of prompt and nonprompt [Formula: see text] production in [Formula: see text] and [Formula: see text] collisions at [Formula: see text].

This paper reports the measurement of [Formula: see text] meson production in proton-proton ([Formula: see text]) and proton-lead ([Formula: see text]) collisions at a center-of-mass energy per nucleon pair of [Formula: see text] by the CMS experiment at the LHC. The data samples used in the analysis correspond to integrated luminosities of 28[Formula: see text] and 35[Formula: see text] for [Formula: see text] and [Formula: see text] collisions, respectively. Prompt and nonprompt [Formula: see text] mesons, the latter produced in the decay of [Formula: see text] hadrons, are measured in their dimuon decay channels. Differential cross sections are measured in the transverse momentum range of [Formula: see text], and center-of-mass rapidity ranges of [Formula: see text] ([Formula: see text]) and [Formula: see text] ([Formula: see text]). The nuclear modification factor, [Formula: see text], is measured as a function of both [Formula: see text] and [Formula: see text]. Small modifications to the [Formula: see text] cross sections are observed in [Formula: see text] relative to [Formula: see text] collisions. The ratio of [Formula: see text] production cross sections in [Formula: see text]-going and Pb-going directions, [Formula: see text], studied as functions of [Formula: see text] and [Formula: see text], shows a significant decrease for increasing transverse energy deposited at large pseudorapidities. These results, which cover a wide kinematic range, provide new insight on the role of cold nuclear matter effects on prompt and nonprompt [Formula: see text] production

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