CMS-PAS-QCD-10-024 | https://cdsweb.cern.ch/record/1341853?ln=en
Pseudorapidity distributions of charged particles in $pp$ collisions at $\sqrt{s} = 0.9$ and 7\;TeV with at least one central charged particle.
Spires | JHEP 1111 148 | doi:10.1007/JHEP11(2011)148 | arXiv:hep-ex/1110.0211
Forward energy flow measured by CMS at $\sqrt{s} = 0.9$ and 7 TeV in MB and dijet events.
Spires | J. High Energy Phys 09 (2011) 109
A measurement of the underlying activity in scattering processes with a hard scale in the several-GeV region is performed in proton-proton collisions at Energies of 0.9 and 7\;TeV, using data collected by the CMS experiment at the LHC. The production of charged particles with pseudorapidity |eta| < 2 and transverse momentum $p_\perp > 0.5$\;GeV/$c$ is studied in the azimuthal region transverse to that of the leading set of charged particles forming a track-jet. Various comparisons are made between the two different energies and also beteen two sets of cuts on p_\perp for leading track jet p_\perp-leading $> 3$\;GeV and pT-leading $> 20$\;GeV. The activity is studied using 5 types of plots. Two profile plots for the multiplicity of charged particles and the scalar sum of p_\perp. and three distributions for the two previous quantities as well as p_\perp for all the particles in the transverse region.
Spires | J. High Energy Phys. 01 (2011) 079 | doi:10.1007/JHEP01(2011)079 | arXiv:1011.5531 [hep-ex]
Measurements of primary charged hadron multiplicity distributions are presented for non-single-diffractive events in proton-proton collisions at centre-of-mass energies of $\sqrt{s} = 0.9$, 2.36, and 7 TeV, in five pseudorapidity ranges from $|\eta| < 0.5$ to $|\eta| < 2.4$. The data were collected with the minimum-bias trigger of the CMS experiment during the LHC commissioning runs in 2009 and the 7 TeV run in 2010. The average transverse momentum as a function of the multiplicity is also presented. The measurement of higher-order moments of the multiplicity distribution confirms the violation of Koba-Nielsen-Olesen scaling that has been observed at lower energies.
Spires | Phys.Rev.Lett.105:022002,2010 | doi:10.1103/PhysRevLett.105.022002 | arXiv:1005.3299 [hep-ex]
Charged particle spectra are measured in proton-proton collisions at center-of-mass energies 7000 GeV. The spectra are normalized to all non-single-diffractive (NSD) events using corrections for trigger and selection efficiency, acceptance, and branching ratios. There are transverse-momentum ($p_\perp$) spectra from 0.1 to 2 GeV in bins of pseudorapidity ($\eta$) and the $p_\perp$ spectrum from 0.1 to 6 GeV for $|\eta| < 2.4$. The $\eta$ spectra come from the average of three methods and cover $|\eta| < 2.5$ and are corrected to include all $p_\perp$. The data were corrected according to the SD/DD/ND content of the CMS trigger, as predicted by PYTHIA6. The uncertainties connected with correct or incorrect modelling of diffraction were included in the systematic errors.
Spires | arXiv:1201.2808 [hep-ex]
Pseudorapidity gap distributions in proton-proton collisions at $\sqrt{s} = 7$ TeV are studied using a minimum bias data sample with an integrated luminosity of 7.1 inverse microbarns. Cross sections are measured differentially in terms of $\Delta \eta_F$, the larger of the pseudorapidity regions extending to the limits of the ATLAS sensitivity, at $\eta = \pm 4.9$, in which no final state particles are produced above a transverse momentum threshold $p_\perp$ cut. The measurements span the region $0 < \Delta \eta_F < 8$ for $200 < p_T\text{ cut} < 800\;\text{MeV}$. At small $\Delta \eta_F$, the data test the reliability of hadronisation models in describing rapidity and transverse momentum fluctuations in final state particle production. The measurements at larger gap sizes are dominated by contributions from the single diffractive dissociation process ($pp \to Xp$), enhanced by double dissociation ($pp \to XY$) where the invariant mass of the lighter of the two dissociation systems satisfies $M_Y \lesssim 7\;\text{GeV}$. The resulting cross section is $\mathrm{d} \sigma / \mathrm{d} \Delta \eta_F \sim 1$ mb for $\Delta \eta_F \gtrsim 3$. The large rapidity gap data are used to constrain the value of the pomeron intercept appropriate to triple Regge models of soft diffraction. The cross section integrated over all gap sizes is compared with other LHC inelastic cross section measurements.
Spires | arXiv:1103.1816
Underlying event measurements with the ATLAS detector at the LHC at center-of-mass energies of 900 GeV and 7 TeV, using calorimeter clusters rather than charged tracks.
Spires | arXiv:1012.5104
Measurements from proton-proton collisions at centre-of-mass energies of $\sqrt{s} = 0.9$, 2.36, and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase-space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections.
Spires | arXiv:1012.0791
The underlying event measurements with the ATLAS detector at the LHC at the center of mass energies of 900 GeV and 7 TeV. The observables sensitive to the underlying event, i.e the charged particle density and charged pT sum, as well as their standard deviations and the average pT, are measured as functions of the leading track. A track pT cut of 500 MeV is applied for most observables, but the main profile plots are also shown for a lower track cut of 100 MeV, which includes much more of the soft cross-section. The angular distribution of the charged tracks with respect to the leading track is also studied, as are the correlation between mean transverse momentum and charged particle multiplicity, and the `plateau' height as a function of the leading track $|\eta|$.
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