The charged particle transverse momentum spectra in the midrapidity and forward pseudorapidity ranges are presented for pPb collisions at $\sqrt{s_{\rm NN}}=5.02$~TeV. The data sample corresponding to an integrated luminosity of 26~${\rm nb}^{-1}$ was collected with the CMS detector at the LHC. The nuclear modification factor is measured at midrapidity by normalizing the measured pPb spectrum to a pp reference spectrum constructed from previous measurements. In addition, the asymmetries in the charged particle yields between equivalent positive and negative pseudorapidity ranges in the center-of-mass frame are presented as a function of transverse momentum.
Invariant charged particle differential yield.
Invariant charged particle differential yield.
Invariant charged particle differential yield.
Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.
Isolated photon spectra for PB PB collisions in 3 centrality ranges.
Isolated photon spectra for PB PB collisions in the full centrality range.
Isolated photon spectra for P P collisions.
A search for Z bosons in the mu^+mu^- decay channel has been performed in PbPb collisions at a nucleon-nucleon centre of mass energy = 2.76 TeV with the CMS detector at the LHC, in a 7.2 inverse microbarn data sample. The number of opposite-sign muon pairs observed in the 60--120 GeV/c2 invariant mass range is 39, corresponding to a yield per unit of rapidity (y) and per minimum bias event of (33.8 ± 5.5 (stat) ± 4.4 (syst)) 10^{-8}, in the |y|<2.0 range. Rapidity, transverse momentum, and centrality dependencies are also measured. The results agree with next-to-leading order QCD calculations, scaled by the number of incoherent nucleon-nucleon collisions.
The dimuon yield from Z0 decays per unit rapidity and per unit minumum bias event in the range |yrap| < 2.0.
The dimuon yield from Z0 decays per unit rapidity and per unit minumum bias event as a function of rapidity, and the nuclear modification factor RAA derived by using a POWHEG proton-proton reference.
The dimuon yield from Z0 decays per unit rapidity and per unit minumum bias event as a function of transverse momentum, and the nuclear modificationfactor RAA derived by using a POWHEG proton-proton reference.
The nuclear modification factor RAA and the azimuthal anisotropy coefficient v[2] of prompt and nonprompt (i.e. those from decays of b hadrons) J/psi mesons, measured from PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV at the LHC, are reported. The results are presented in several event centrality intervals and several kinematic regions, for transverse momenta pt > 6.5 GeV/c and rapidity abs(y) < 2.4, extending down to pt = 3 GeV/c in the 1.6 < abs(y) < 2.4 range. The v[2] of prompt J/psi is found to be nonzero, but with no strong dependence on centrality, rapidity, or pt over the full kinematic range studied. The measured v[2] of nonprompt J/psi is consistent with zero. The RAA of prompt J/psi exhibits a suppression that increases from peripheral to central collisions but does not vary as a function of either y or pt in the fiducial range. The nonprompt J/psi RAA shows a suppression which becomes stronger as rapidity or pt increase. The v[2] and nuclear suppression of open and hidden charm, and of open charm and beauty, are compared.
Prompt J/$\psi$ $v_{2}$ as a function of centrality. The average ${N}_{\rm part}$ values correspond to events flatly distributed across centrality.
Prompt J/$\psi$ $v_{2}$ as a function of centrality. The average ${N}_{\rm part}$ values correspond to events flatly distributed across centrality.
Prompt J/$\psi$ $v_{2}$ as a function of rapidity.
The spectra of charged particles produced within the pseudorapidity window abs(eta) < 1 at sqrt(s[NN]) = 5.02 TeV are measured using 404 inverse microbarns of PbPb and 27.4 inverse picobarns of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0.5 < pt < 400 GeV in pp and 0.7 < pt < 400 GeV in PbPb collisions. The corresponding nuclear modification factor, R[AA], is measured in bins of collision centrality. The R[AA] in the 5% most central collisions shows a maximal suppression by a factor of 7-8 in the pt region of 6-9 GeV. This dip is followed by an increase, which continues up to the highest pt measured, and approaches unity in the vicinity of pt = 200 GeV. The R[AA] is compared to theoretical predictions and earlier experimental results at lower collision energies. The newly measured pp spectrum is combined with the pPb spectrum previously published by the CMS Collaboration to construct the pPb nuclear modification factor, R[pA], up to 120 GeV. For pt > 20 GeV, R[pA] exhibits weak momentum dependence and shows a moderate enhancement above unity.
Charged-particle per-event yields measured in 0-5% PbPb centrality class.
Charged-particle per-event yields measured in 0-5% PbPb centrality class.
Charged-particle per-event yields measured in 5-10% PbPb centrality class.
The production yields of Upsilon(1S), Upsilon(2S), and Upsilon(3S) quarkonium states are measured through their decays into muon pairs in the CMS detector, in PbPb and pp collisions at the centre-of-mass energy per nucleon pair of 2.76 TeV. The data correspond to integrated luminosities of 166 inverse microbarns and 5.4 inverse picobarns for PbPb and pp collisions, respectively. Differential production cross sections are reported as functions of Upsilon rapidity y up to 2.4, and transverse momentum pT up to 20 GeV/c. A strong centrality-dependent suppression is observed in PbPb relative to pp collisions, by factors of up to approximately 2 and 8, for the Upsilon(1S) and Upsilon(2S) states, respectively. No significant dependence of this suppression is observed as a function of y or pT. The Upsilon(3S) state is not observed in PbPb collisions, which corresponds to a suppression for the centrality-integrated data by at least a factor of approximately 7 at a 95% confidence level. The observed suppression is in agreement with theoretical scenarios modeling the sequential melting of quarkonium states in a quark gluon plasma.
Differential cross section for Y(1S) states as a function of their transverse momentum and per unit of rapidity in pp collisions. Statistical (systematic) uncertainties are displayed as error bars (boxes). Global relative uncertainties of 3.7% are not displayed.
Differential cross section for Y(1S) states as a function of their transverse momentum and per unit of rapidity in pp collisions. Statistical (systematic) uncertainties are displayed as error bars (boxes). Global relative uncertainties of 3.7% are not displayed.
Differential cross section for Y(2S) states as a function of their transverse momentum and per unit of rapidity in pp collisions. Statistical (systematic) uncertainties are displayed as error bars (boxes). Global relative uncertainties of 3.7% are not displayed.
The differential yields of charged particles having pseudorapidity within $|\eta|<$ 1 are measured using xenon-xenon (XeXe) collisions at $\sqrt{s_\mathrm{NN}}$ = 5.44 TeV. The data, corresponding to an integrated luminosity of 3.42 $\mu$b$^{-1}$, were collected in 2017 by the CMS experiment at the LHC. The yields are reported as functions of collision centrality and transverse momentum, $p_\mathrm{T}$, from 0.5 to 100 GeV. A previously reported $p_\mathrm{T}$ spectrum from proton-proton collisions at $\sqrt{s}$ = 5.02 TeV is used for comparison after correcting for the difference in center-of-mass energy. The nuclear modification factors using this reference, $R_\mathrm{AA}^*$, are constructed and compared to previous measurements and theoretical predictions. In head-on collisions, the $R_\mathrm{AA}^*$ has a value of 0.17 in the $p_\mathrm{T}$ range of 6-8 GeV, but increases to approximately 0.7 at 100 GeV. Above $\approx$ 6 GeV, the XeXe data show a notably smaller suppression than previous results for lead-lead (PbPb) collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV when compared at the same centrality (i.e., the same fraction of total cross section). However, the XeXe suppression is slightly greater than that for PbPb in events having a similar number of participating nucleons.
The per-event differential invariant yield of charged particles having |eta|<1 in XeXe collisions at sqrt(s_NN)=5.44 TeV. The first systematic uncertainty describes uncertainties that are not fully correlated across points, while the second systematic uncertainty is a normalization uncertainty that is fully correlated across all points. Bins where no data point has been reported are denoted as 'empty'.
The per-event differential invariant yield of charged particles having |eta|<1 in pp collisions at sqrt(s)=5.44 TeV, after extrpolation from 5.02 TeV data. The first systematic uncertainty describes uncertainties that are not fully correlated across points, while the second systematic uncertainty is a normalization uncertainty that is fully correlated across all points. The data is measured and extrapolated as a differential cross section, and transformed into a differential yield using an inelastic cross-section of 70 mb.
The nuclear modification factor of charged particles having |eta|<1 in XeXe collisions at sqrt(s_NN)=5.44 TeV. The first systematic uncertainty describes uncertainties that are not fully correlated across points, while the second systematic uncertainty is a normalization uncertainty that is fully correlated across all points. Bins where no data point has been reported are denoted as 'empty'.
Inclusive jet spectra from pp and PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV, collected with the CMS detector at the LHC, are presented. Jets are reconstructed with three different distance parameters (R = 0.2, 0.3, and 0.4) for transverse momentum (pT) greater than 70 GeV and pseudorapidity abs(eta) < 2. Next-to-leading-order quantum chromodynamic calculations with non-perturbative corrections are found to over-predict jet production cross sections in pp for small distance parameters. The jet nuclear modification factors for PbPb compared to pp collisions, show a steady decrease from peripheral to central events, along with a weak dependence on the jet pT. They are found to be independent of the distance parameter in the measured kinematic range.
Raw subtracted $p_T$ for jets reconstructed in PbPb collisions (in different centrality bins) with the anti-k$_T$ algorythm with distance parameter $R=0.3$, in the range $70< p_{T} < 80$GeV/c and $|\eta|<2$. Quantity found by taking the difference of the sum of PF candidates within the jet cone and raw jet $p_T$.
Raw subtracted $p_T$ for jets reconstructed in PbPb collisions (in different centrality bins) with the anti-k$_T$ algorythm with a distance parameter $R=0.3$, in the range $110< p_{T} < 130$GeV/c and $|\eta|<2$. Quantity found by taking the difference of the sum of PF candidates within the jet cone and raw jet $p_T$.
Average raw subtracted $p_T$ for PF jets reconstructed in PbPb collisions (in different centrality bins) with the anti-k$_T$ algorythm with a distance parameter $R=0.3$, in $|\eta|<0.2$.
The transverse energy ($E_\mathrm{T}^{\gamma}$) spectra of photons isolated from other particles are measured using proton-proton (pp) and lead-lead (PbPb) collisions at the LHC at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV with integrated luminosities of 27.4 pb$^{-1}$and 404 $\mu$b$^{-1}$ for pp and PbPb data, respectively. The results are presented for photons with 25 $<$ $E_\mathrm{T}^{\gamma}$ $<$ 200 GeV in the pseudorapidity range $|\eta|$ $<$ 1.44, and for different centrality intervals for PbPb collisions. Photon production in PbPb collisions is consistent with that in pp collisions scaled by the number of binary nucleon-nucleon collisions, demonstrating that photons do not interact with the quark-gluon plasma. Therefore, isolated photons can provide information about the initial energy of the associated parton in photon+jet measurements. The results are compared with predictions from the next-to-leading-order JETPHOX generator for different parton distribution functions (PDFs) and nuclear PDFs (nPDFs). The comparisons can help to constrain the nPDFs global fits.
Isolated photon spectra measured as a function of $E_{T}^{\gamma}$ for 0–10%, 10–30%, 30– 50%, 50–100%, and 0–100% PbPb collisions (scaled by $T_{AA}$) at 5.02TeV.
Isolated photon cross section measured as a function of $E_{T}^{\gamma}$ in pp collisions at 5.02TeV.
Nuclear modification factors $R_{AA}$ as a function of $E_{T}^{\gamma}$ measured in the 0–10%, 10–30%, 30–50%, and 50–100% centrality ranges in PbPb.
The differential cross sections of $\Lambda_\mathrm{c}^+$ baryon production are measured via the exclusive decay channel $\Lambda_\mathrm{c}^+ \to $pK$^-\pi^+$, as a function of transverse momentum ($p_\mathrm{T}$) in proton-proton (pp) and lead-lead (PbPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV with the CMS detector at the LHC. The measurement is performed within the $\Lambda_\mathrm{c}^+$ rapidity interval $|y|<$1.0 in the $p_\mathrm{T}$ range of 5-20 GeV/$c$ in pp and 10-20 GeV/$c$ in PbPb collisions. The observed yields of $\Lambda_\mathrm{c}^+$ for $p_\mathrm{T}$ of 10-20 GeV/$c$ suggest a possible suppression in central PbPb collisions compared to pp collisions. The $\Lambda_\mathrm{c}^+/$D$^0$ production ratio in pp collisions is compared to theoretical models. In PbPb collisions, this ratio is consistent with the result from pp collisions in their common $p_\mathrm{T}$ range.
The $p_{T}$-differential cross sections for inclusive $\Lambda_{c}^{+}$ production in pp collisions. The uncertainties associated with the $\Lambda_{c}^{+} \to pK^{-}\pi^{+}$ branching fraction and subresonant contributions, the luminosity and the nonprompt fraction contribute only to the overall normalization and are labeled global uncertainties ($21\%$).
The $T_{AA}$-scaled yields for inclusive $\Lambda_{c}^{+}$ baryon in three centrality regions of PbPb collisions. The uncertainties associated with the $\Lambda_{c}^{+} \to pK^{-}\pi^{+}$ branching fraction and subresonant contributions, the MB selection efficiency and the nonprompt fraction contribute only to the overall normalization and are labeled global uncertainties ($31\%$).
The nuclear modification factor $R_{AA}$ versus $\langle N_\text{part} \rangle$ for inclusive $\Lambda_{c}^{+}$ production in the centrality range $0-100\%$, $0-30\%$ and $30-100\%$. The systematic uncertainties include the PbPb systematic uncertainties associated with the signal extraction, $p_{T}$ spectrum, selection criteria, track reconstruction, and $T_{AA}$. The pp uncertainty includes the same uncertainties for the pp data (except for $T_{AA}$) plus the uncertainties in pp yield and luminosity. The global PbPb uncertainty includes the uncertainty from the nonprompt fraction(accounting for a partial cancelation between pp and PbPb) and MB selection efficiency.
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