Copyright ~1975-Present, HEPData | Powered by Invenio, funded by STFC, hosted and originally developed at CERN, supported and further developed at IPPP Durham.
The production of J/psi mesons is studied in pp collisions at sqrt(s)=7 TeV with the CMS experiment at the LHC. The measurement is based on a dimuon sample corresponding to an integrated luminosity of 314 inverse nanobarns. The J/psi differential cross section is determined, as a function of the J/psi transverse momentum, in three rapidity ranges. A fit to the decay length distribution is used to separate the prompt from the non-prompt (b hadron to J/psi) component. Integrated over J/psi transverse momentum from 6.5 to 30 GeV/c and over rapidity in the range |y| < 2.4, the measured cross sections, times the dimuon decay branching fraction, are 70.9 \pm 2.1 (stat.) \pm 3.0 (syst.) \pm 7.8(luminosity) nb for prompt J/psi mesons assuming unpolarized production and 26.0 \pm 1.4 (stat.) \pm 1.6 (syst.) \pm 2.9 (luminosity) nb for J/psi mesons from b-hadron decays.
The charge ratio, Rμ=Nμ+/Nμ-, for cosmogenic multiple-muon events observed at an underground depth of 2070 mwe has been measured using the magnetized MINOS Far Detector. The multiple-muon events, recorded nearly continuously from August 2003 until April 2012, comprise two independent data sets imaged with opposite magnetic field polarities, the comparison of which allows the systematic uncertainties of the measurement to be minimized. The multiple-muon charge ratio is determined to be Rμ=1.104±0.006(stat)-0.010+0.009(syst). This measurement complements previous determinations of single-muon and multiple-muon charge ratios at underground sites and serves to constrain models of cosmic-ray interactions at TeV energies.
Results on $\phi$ meson production in inelastic p+p collisions at CERN SPS energies are presented. They are derived from data collected by the NA61/SHINE fixed target experiment, by means of invariant mass spectra fits in the $\phi \to K^+K^-$ decay channel. They include the first ever measured double differential spectra of $\phi$ mesons as a function of rapidity $y$ and transverse momentum $p_T$ for proton beam momenta of 80 GeV/c and 158 GeV/c, as well as single differential spectra of $y$ or $p_T$ for beam momentum of 40 GeV/c. The corresponding total $\phi$ yields per inelastic p+p event are obtained. These results are compared with existing data on $\phi$ meson production in p+p collisions. The comparison shows consistency but superior accuracy of the present measurements. The emission of $\phi$ mesons in p+p reactions is confronted with that occurring in Pb+Pb collisions, and the experimental results are compared with model predictions. It appears that none of the considered models can properly describe all the experimental observables.
Measurements of strange hadron (K0s, Lambda + anti-Lambda, and Xi+ + Xi-) transverse momentum spectra in pp, pPb, and PbPb collisions are presented over a wide range of rapidity and event charged-particle multiplicity. The data were collected with the CMS detector at the CERN LHC in pp collisions at sqrt(s) = 7 TeV, pPb collisions at sqrt(s[NN]) = 5.02 TeV, and PbPb collisions at sqrt(s[NN]) = 2.76 TeV. The average transverse kinetic energy is found to increase with multiplicity, at a faster rate for heavier strange particle species in all systems. At similar multiplicities, the difference in average transverse kinetic energy between different particle species is observed to be larger for pp and pPb events than for PbPb events. In pPb collisions, the average transverse kinetic energy is found to be slightly larger in the Pb-going direction than in the p-going direction for events with large multiplicity. The spectra are compared to models motivated by hydrodynamics.
<p>The ratio between the prompt <inline-formula><mml:math display="inline"><mml:mi>ψ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>2</mml:mn><mml:mi>S</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> and <inline-formula><mml:math display="inline"><mml:mi>J</mml:mi><mml:mo stretchy="false">/</mml:mo><mml:mi>ψ</mml:mi></mml:math></inline-formula> yields, reconstructed via their decays into <inline-formula><mml:math display="inline"><mml:msup><mml:mi>μ</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>μ</mml:mi><mml:mo>-</mml:mo></mml:msup></mml:math></inline-formula>, is measured in Pb-Pb and <inline-formula><mml:math display="inline"><mml:mi>p</mml:mi></mml:math></inline-formula>-<inline-formula><mml:math display="inline"><mml:mi>p</mml:mi></mml:math></inline-formula> collisions at <inline-formula><mml:math display="inline"><mml:mrow><mml:msqrt><mml:mrow><mml:msub><mml:mrow><mml:mi>s</mml:mi></mml:mrow><mml:mrow><mml:mi>N</mml:mi><mml:mi>N</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:msqrt><mml:mo>=</mml:mo><mml:mn>2.76</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:mrow></mml:math></inline-formula>. The analysis is based on Pb-Pb and <inline-formula><mml:math display="inline"><mml:mi>p</mml:mi></mml:math></inline-formula>-<inline-formula><mml:math display="inline"><mml:mi>p</mml:mi></mml:math></inline-formula> data samples collected by CMS at the Large Hadron Collider, corresponding to integrated luminosities of <inline-formula><mml:math display="inline"><mml:mrow><mml:mn>150</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>μ</mml:mi><mml:msup><mml:mrow><mml:mi mathvariant="normal">b</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> and <inline-formula><mml:math display="inline"><mml:mrow><mml:mn>5.4</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mrow><mml:mi>pb</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula>, respectively. The double ratio of measured yields <inline-formula><mml:math display="inline"><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mrow><mml:mi>N</mml:mi></mml:mrow><mml:mrow><mml:mi>ψ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>2</mml:mn><mml:mi>S</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:msub><mml:mo stretchy="false">/</mml:mo><mml:msub><mml:mrow><mml:mi>N</mml:mi></mml:mrow><mml:mrow><mml:mi>J</mml:mi><mml:mo stretchy="false">/</mml:mo><mml:mi>ψ</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mrow><mml:mi>Pb</mml:mi><mml:mtext>-</mml:mtext><mml:mi>Pb</mml:mi></mml:mrow></mml:msub><mml:mo stretchy="false">/</mml:mo><mml:mspace linebreak="goodbreak"/><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mrow><mml:mi>N</mml:mi></mml:mrow><mml:mrow><mml:mi>ψ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>2</mml:mn><mml:mi>S</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:msub><mml:mo stretchy="false">/</mml:mo><mml:msub><mml:mrow><mml:mi>N</mml:mi></mml:mrow><mml:mrow><mml:mi>J</mml:mi><mml:mo stretchy="false">/</mml:mo><mml:mi>ψ</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mrow><mml:mi>p</mml:mi><mml:mtext/><mml:mtext>-</mml:mtext><mml:mi>p</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula> is computed in three Pb-Pb collision centrality bins and two kinematic ranges: one at midrapidity, <inline-formula><mml:math display="inline"><mml:mrow><mml:mo stretchy="false">|</mml:mo><mml:mi>y</mml:mi><mml:mo stretchy="false">|</mml:mo></mml:mrow><mml:mo><</mml:mo><mml:mn>1.6</mml:mn></mml:math></inline-formula>, covering the transverse momentum range <inline-formula><mml:math display="inline"><mml:mrow><mml:mn>6.5</mml:mn><mml:mo><</mml:mo><mml:msub><mml:mrow><mml:mi>p</mml:mi></mml:mrow><mml:mrow><mml:mi>T</mml:mi></mml:mrow></mml:msub><mml:mo><</mml:mo><mml:mn>30</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>GeV</mml:mi><mml:mo>/</mml:mo><mml:mi>c</mml:mi></mml:mrow></mml:math></inline-formula>, and the other at forward rapidity, <inline-formula><mml:math display="inline"><mml:mn>1.6</mml:mn><mml:mo><</mml:mo><mml:mrow><mml:mo stretchy="false">|</mml:mo><mml:mi>y</mml:mi><mml:mo stretchy="false">|</mml:mo></mml:mrow><mml:mo><</mml:mo><mml:mn>2.4</mml:mn></mml:math></inline-formula>, extending to lower <inline-formula><mml:math display="inline"><mml:msub><mml:mi>p</mml:mi><mml:mi>T</mml:mi></mml:msub></mml:math></inline-formula> values, <inline-formula><mml:math display="inline"><mml:mrow><mml:mn>3</mml:mn><mml:mo><</mml:mo><mml:msub><mml:mrow><mml:mi>p</mml:mi></mml:mrow><mml:mrow><mml:mi>T</mml:mi></mml:mrow></mml:msub><mml:mo><</mml:mo><mml:mn>30</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>GeV</mml:mi><mml:mo>/</mml:mo><mml:mi>c</mml:mi></mml:mrow></mml:math></inline-formula>. The centrality-integrated double ratio changes from <inline-formula><mml:math display="inline"><mml:mrow><mml:mn>0.45</mml:mn><mml:mo>±</mml:mo><mml:mn>0.13</mml:mn><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mtext>stat</mml:mtext><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mo>±</mml:mo><mml:mn>0.07</mml:mn><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mtext>syst</mml:mtext><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> in the first range to <inline-formula><mml:math display="inline"><mml:mn>1.67</mml:mn><mml:mo>±</mml:mo><mml:mn>0.34</mml:mn><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mtext>stat</mml:mtext><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mo>±</mml:mo><mml:mn>0.27</mml:mn><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mtext>syst</mml:mtext><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math></inline-formula> in the second. This difference is most pronounced in the most central collisions.</p>
A measurement is presented of the ratio of the inclusive 3-jet cross section to the inclusive 2-jet cross section as a function of the average transverse momentum, <pT[1,2]>, of the two leading jets in the event. The data sample was collected during 2011 at a proton-proton centre-of-mass energy of 7 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 5.0 inverse femtobarns. The strong coupling constant at the scale of the Z boson mass is determined to be alphaS[MZ] = 0.1148 +/- 0.0014 (exp.) +/- 0.0018 (PDF) +/- 0.0050 (theory), by comparing the ratio in the range 0.42 < <pT[1,2]> < 1.39 TeV to the predictions of perturbative QCD at next-to-leading order. This is the first determination of alphaS[MZ] from measurements at momentum scales beyond 0.6 TeV. The predicted ratio depends only indirectly on the evolution of the parton distribution functions of the proton such that this measurement also serves as a test of the evolution of the strong coupling constant. No deviation from the expected behaviour is observed.
The relative modification of the prompt psi(2S) and J/psi yields from pp to PbPb collisions, at the center of mass energy of 5.02 TeV per nucleon pair, is presented. The analysis is based on pp and PbPb data samples collected by the CMS experiment at the LHC in 2015, corresponding to integrated luminosities of 28.0 inverse picobarns and 464 inverse microbarns, respectively. The double ratio of measured yields of prompt charmonia reconstructed through their decays into muon pairs, (N[psi(2S)]/N[J/psi])[PbPb]/ (N[psi(2S)]/N[J/psi])[pp], is determined as a function of PbPb collision centrality and charmonium transverse momentum pt, in two kinematic intervals: abs(y) < 1.6 covering 6.5 < pt < 30GeV/c and 1.6 < abs(y) < 2.4 covering 3 <pt< 30GeV/c. The centrality-integrated double ratios are 0.36 +/- 0.08 (stat) +/-0.05 (syst) in the first interval and 0.24 +/- 0.22 (stat) +/- 0.09 (syst) in the second. The double ratio is lower than unity in all the measured bins, suggesting that the psi(2S) yield is more suppressed than the J/psi yield in the explored phase space.
The relative yields of Upsilon mesons produced in pp and PbPb collisions at sqrt(s[NN]) = 5.02 TeV and reconstructed via the dimuon decay channel are measured using data collected by the CMS experiment. Double ratios are formed by comparing the yields of the excited states, Upsilon(2S) and Upsilon(3S), to the ground state, Upsilon(1S), in both PbPb and pp collisions at the same center-of-mass energy. The double ratios, [Upsilon(nS)/Upsilon(1S)](PbPb)/[Upsilon(nS)/Upsilon(1S)](pp), are measured to be 0.308 +/- 0.055 (stat) +/- 0.019 (syst) for the Upsilon(2S) and less than 0.26 at 95% confidence level for the Upsilon(3S). No significant Upsilon(3S) signal is found in the PbPb data. The double ratios are studied as a function of collision centrality, as well as dimuon transverse momentum and rapidity. No significant dependencies are observed.
The production of W$^\pm$ bosons is studied in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_\mathrm{NN}} =$ 8.16 TeV. Measurements are performed in the W$^\pm \to \mu^\pm\nu_\mu$ channel using a data sample corresponding to an integrated luminosity of 173.4 $\pm$ 8.7 nb$^{-1}$, collected by the CMS Collaboration at the LHC. The number of positively and negatively charged W bosons is determined separately in the muon pseudorapidity region in the laboratory frame $|\eta^\mu_\mathrm{lab}| <$ 2.4 and transverse momentum $p_\mathrm{T}^\mu >$ 25 GeV/$c$. The W$^\pm$ boson differential cross sections, muon charge asymmetry, and the ratios of W$^\pm$ boson yields for the proton-going over the Pb-going beam directions are reported as a function of the muon pseudorapidity in the nucleon-nucleon centre-of-mass frame. The measurements are compared to the predictions from theoretical calculations based on parton distribution functions (PDFs) at next-to-leading-order. The results favour PDF calculations that include nuclear modifications and provide constraints on the nuclear PDF global fits.
Copyright ~1975-Present, HEPData | Powered by Invenio, funded by STFC, hosted and originally developed at CERN, supported and further developed at IPPP Durham.