Charged particle multiplicities in pp interactions at sqrt(s) = 0.9, 2.36, and 7 TeV


All figures in a tar file : PNGs , PDFs
Link to values of the plots at the durham database : link
Link to published version on arxiv : paper

Abstract:
Measurements of primary charged hadron multiplicity distributions are presented for non-single-diffractive events in proton-proton collisions at centre-of-mass energies of √s = 0.9, 2.36, and 7 TeV, in five pseudorapidity ranges from abs(η) < 0.5 to abs(η) < 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 multiplicity distribution at √s = 0.9 TeV is in agreement with previous measurements. At higher energies the increase of the mean multiplicity with √s is underestimated by most event generators. 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.

MC Tunes:
In the following plots we shown the following MC tunes: PYTHIA6 D6T and PYTHIA8.135 Tune1 as well as PHOJET

Figure Abbreviated Caption
nch_unfolding_7000GeV_NONE.png Figure 1:
A comparison of the uncorrected and fully corrected multiplicity distribution at sqrt(s) = 7 TeV for abs(η ) < 2.4 . The uncertainties before corrections are statistical only, while after corrections the statistical and systematic uncertainties are added in quadrature.
nch_900GeV_pt0_NONE_logY.pngnch_2360GeV_pt0_NONE_logY.pngnch_7000GeV_pt0_NONE_logY.png Figure 2:
The fully corrected charged hadron multiplicity spectrum for abs(η) < 0.5, 1.0, 1.5, 2.0, and 2.4, (a) at sqrt(s) = 0.9 TeV, (b) 2.36 TeV, and (c) 7 TeV, compared with other measurements in the same η interval and at the same centre-of-mass energy. For clarity, results in different pseudorapidity intervals are scaled by powers of 10 as given in the plots. The error bars are the statistical and systematic uncertainties added in quadrature.
nch_models_pt0_NONE_logY.pngnch_models_pt500_NONE_logY.png Figure 3:
The charged hadron multiplicity distributions with abs(η) < 2.4 for (a) pT > 0 and (b) pT > 500 MeV/c at sqrt(s) = 0.9, 2.36, and 7 TeV, compared to two different PYTHIA models and the PHOJET model. For clarity, results for different centre-of-mass energies are scaled by powers of 10 as given in the plots.
mptstack_eta24_NONE.png Figure 4:
(a) A comparison of pT versus n for abs(η) < 2.4 with two different PYTHIA models and the PHOJET model at sqrt(s) = 0.9, 2.36, and 7 TeV. For clarity, results for different energies are shifted by the values of a shown in the plots. Fits to the high-multiplicity part (n > 15) with a linear form in n are superimposed. (b) The ratios of the higher-energy data to the fit at sqrt(s) = 0.9 TeV indicate the approximate energy independence of pT at fixed n.
kno_eta25_no2360_NONE_logY.png kno_eta05_no2360_NONE_logY.png Figure 5:
The charged hadron multiplicity distributions in KNO form at two pseudorapidity intervals, (a) abs(η) < 2.4 and (b) abs(η) < 0.5.
Cmoments_cut5.png Cmoments_cut9.png Figure 6:
Fits of the log s dependence of the normalised moments Cq of the multiplicity distribution for (a) abs(η) < 2.4 (assuming linear dependence) and (b) abs(η) < 0.5 (assuming no dependence), including data from lower energy experiments. For sqrt(s) = 0.9 TeV, data from experiments other than CMS were drawn shifted to lower sqrt(s) for clarity.
nchmean_cut5.png Figure 7:
The evolution of the mean charge multiplicity with the centre-of-mass energy for abs(η) < 2.4, including data from lower-energy experiments for abs(η) < 2.5. The data are compared with predictions from three analytical Regge-inspired models and from a saturation model.

-- RomainRougny - 06-Apr-2011

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf Cmoments_cut5.pdf r1 manage 7.9 K 2011-04-06 - 13:13 RomainRougny  
PNGpng Cmoments_cut5.png r1 manage 40.7 K 2011-04-06 - 13:08 RomainRougny  
PDFpdf Cmoments_cut9.pdf r1 manage 5.7 K 2011-04-06 - 13:10 RomainRougny  
PNGpng Cmoments_cut9.png r1 manage 32.4 K 2011-04-06 - 13:07 RomainRougny  
Unknown file formatgz figs_CMS_QCD-10-004_PDF.tar.gz r1 manage 205.4 K 2011-04-06 - 14:21 RomainRougny  
Unknown file formatgz figs_CMS_QCD-10-004_PNG.tar.gz r1 manage 520.6 K 2011-04-06 - 14:22 RomainRougny  
PDFpdf kno_eta05_no2360_NONE_logY.pdf r1 manage 7.9 K 2011-04-06 - 13:10 RomainRougny  
PNGpng kno_eta05_no2360_NONE_logY.png r1 manage 31.8 K 2011-04-06 - 13:07 RomainRougny  
PDFpdf kno_eta25_no2360_NONE_logY.pdf r1 manage 13.1 K 2011-04-06 - 13:10 RomainRougny  
PNGpng kno_eta25_no2360_NONE_logY.png r1 manage 42.9 K 2011-04-06 - 13:07 RomainRougny  
PDFpdf mptstack_eta24_NONE.pdf r1 manage 37.8 K 2011-04-06 - 13:09 RomainRougny  
PNGpng mptstack_eta24_NONE.png r1 manage 71.6 K 2011-04-06 - 13:07 RomainRougny  
PDFpdf nch_2360GeV_pt0_NONE_logY.pdf r1 manage 21.0 K 2011-04-06 - 13:10 RomainRougny  
PNGpng nch_2360GeV_pt0_NONE_logY.png r1 manage 56.0 K 2011-04-06 - 13:06 RomainRougny  
PDFpdf nch_7000GeV_pt0_NONE_logY.pdf r1 manage 34.2 K 2011-04-06 - 13:12 RomainRougny  
PNGpng nch_7000GeV_pt0_NONE_logY.png r1 manage 26.4 K 2011-04-06 - 13:06 RomainRougny  
PDFpdf nch_900GeV_pt0_NONE_logY.pdf r1 manage 23.3 K 2011-04-06 - 13:09 RomainRougny  
PNGpng nch_900GeV_pt0_NONE_logY.png r1 manage 65.4 K 2011-04-06 - 13:07 RomainRougny  
PDFpdf nch_models_pt0_NONE_logY.pdf r1 manage 36.3 K 2011-04-06 - 13:12 RomainRougny  
PNGpng nch_models_pt0_NONE_logY.png r1 manage 67.2 K 2011-04-06 - 13:06 RomainRougny  
PDFpdf nch_models_pt500_NONE_logY.pdf r1 manage 24.1 K 2011-04-06 - 13:12 RomainRougny  
PNGpng nch_models_pt500_NONE_logY.png r1 manage 63.9 K 2011-04-06 - 13:05 RomainRougny  
PDFpdf nch_unfolding_7000GeV_NONE.pdf r1 manage 13.2 K 2011-04-06 - 13:12 RomainRougny  
PNGpng nch_unfolding_7000GeV_NONE.png r1 manage 44.3 K 2011-04-06 - 13:06 RomainRougny  
PDFpdf nchmean_cut5.pdf r1 manage 5.7 K 2011-04-06 - 13:12 RomainRougny  
PNGpng nchmean_cut5.png r1 manage 42.3 K 2011-04-06 - 13:07 RomainRougny  
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