The $p_{\rm T}$-differential production cross sections of the prompt (B feed-down subtracted) charmed mesons D$^0$, D$^+$, and D$^{*+}$ in the rapidity range $|y|<0.5$, and for transverse momentum $1< p_{\rm T} <12$ GeV/$c$, were measured in proton-proton collisions at $\sqrt{s} = 2.76$ TeV with the ALICE detector at the Large Hadron Collider. The analysis exploited the hadronic decays D$^0 \rightarrow $K$\pi$, D$^+ \rightarrow $K$\pi\pi$, D$^{*+} \rightarrow $D$^0\pi$, and their charge conjugates, and was performed on a $L_{\rm int} = 1.1$ nb$^{-1}$ event sample collected in 2011 with a minimum-bias trigger. The total charm production cross section at $\sqrt{s} = 2.76$ TeV and at 7 TeV was evaluated by extrapolating to the full phase space the $p_{\rm T}$-differential production cross sections at $\sqrt{s} = 2.76$ TeV and our previous measurements at $\sqrt{s} = 7$ TeV. The results were compared to existing measurements and to perturbative-QCD calculations. The fraction of cdbar D mesons produced in a vector state was also determined.
Production cross section in |y| < 0.5 for prompt D0, D+, and D*+ mesons in pp collisions at sqrt(s) = 2.76 TeV, in transverse momentum intervals. The second (sys) error is the uncertainty on the respective branching ratios.
Visible production cross sections of prompt D mesons for |y|<0.5 in pp collisions at sqrts=2.76 and 7 TeV. The normalization systematic uncertainty of 1.9% (3.5%) at sqrts=2.76 (7) TeV and the decay BR uncertainties are not quoted here.
Production cross sections dsig/dy of D mesons, integrated over all pt for |y|<0.5. The second (sys) error is the from the luminosity uncertainty, the third from the branching-ratio uncertainties and the fourth is from the extrapolation uncertainty.
The transverse momentum ($p_{\mathrm T}$) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC. The $p_{\mathrm T}$ spectra measured near central rapidity in the range $0.5<p_{\mathrm T}<20$ GeV/$c$ exhibit a weak pseudorapidity dependence. The nuclear modification factor $R_{\mathrm{pPb}}$ is consistent with unity for $p_{\mathrm T}$ above 2 GeV/$c$. This measurement indicates that the strong suppression of hadron production at high $p_{\mathrm T}$ observed in Pb-Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.
Normalized differential primary charged particle yield.
pp INEL cross section scaled by nuclear overlap.
Nuclear Modification Factor R_pPb in the central region.
The charged-particle pseudorapidity density measured over 4 units of pseudorapidity in non-single-diffractive (NSD) p-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.02$ TeV is presented. The average value at midrapidity is measured to be $16.81 \pm 0.71$ (syst.), which corresponds to $2.14 \pm 0.17$ (syst.) per participating nucleon. This is 16% lower than in NSD pp collisions interpolated to the same collision energy, and 84% higher than in d-Au collisions at $\sqrt{s_{\rm NN}} = 0.2$ TeV. The measured pseudorapidity density in p-Pb collisions is compared to model predictions, and provides new constraints on the description of particle production in high-energy nuclear collisions.
The pseudorapidity density of charged particles in the lab. frame.
Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < $p_{\rm T}^{\rm assoc}$ < $p_{\rm T}^{\rm trig}$ < 4 GeV/$c$. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and $p_{\rm T}$ bins, and the widths show no significant evolution with event multiplicity or $p_{\rm T}$. These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge.
The Fourier coefficient V2 for different multiplicity classes and overlapping PT_trig and PT_assoc intervals. Note that all multiplicity classes have the values from the 60-100% multiplicity class subtracted.
The Fourier coefficient V3 for different multiplicity classes and overlapping PT_trig and PT_assoc intervals. Note that all multiplicity classes have the values from the 60-100% multiplicity class subtracted.
The near-side ridge yields per unit pseudorapidiy difference between the trigger and associated particle in regions of differing PT_trig and PT_assoc bins for different multiplicity classes. Note that all multiplicity classes have the values from the 60-100% multiplicity class subtracted.
Differential cross sections of charged particles in inelastic pp collisions as a function of $p_{\rm T}$ have been measured at $\sqrt{s}=$ 0.9, 2.76 and 7 TeV at the LHC. The $p_{\rm T}$ spectra are compared to NLO-pQCD calculations. Though the differential cross section for an individual $\sqrt{s}$ cannot be described by NLO-pQCD, the relative increase of cross section with $\sqrt{s}$ is in agreement with NLO-pQCD. Based on these measurements and observations, procedures are discussed to construct pp reference spectra at $\sqrt{s} =$ 2.76 and 5.02 TeV up to $p_{\rm T}$ = 50 GeV/$c$ as required for the calculation of the nuclear modification factor in nucleus-nucleus and proton-nucleus collisions.
The normalized differential primary charged particle cross sections measured at 0.9, 2.76 and 7 TeV centre-of- mass energies. Additional systematic error for 0.9 TeV data: +5.1% -4.0%. Additional systematic error for 2.76 TeV data: +1.9% -1.9%. Additional systematic error for 7.0 TeV data: +3.6% -3.6%.
The ratios of differential cross sections of charged particles at different collisions energies.
The constructed reference P-P spectra for comparison with PB-PB and p-PB spectra.
The average transverse momentum $\langle p_{\rm T}\rangle$ versus the charged-particle multiplicity $N_{\rm ch}$ was measured in p-Pb collisions at a collision energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}}=5.02$ TeV and in pp collisions at collision energies of $\sqrt{s}=0.9$, 2.76, and 7 TeV in the kinematic range $0.15<p_{\rm T}<10.0$ GeV/$c$ and $|\eta|<0.3$ with the ALICE apparatus at the LHC. These data are compared to results in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV at similar charged-particle multiplicities. In pp and p-Pb collisions, a strong increase of $\langle p_{\rm T}\rangle$ with $N_{\rm ch}$ is observed, which is much stronger than that measured in Pb-Pb collisions. For pp collisions, this could be attributed, within a model of hadronizing strings, to multiple-parton interactions and to a final-state color reconnection mechanism. The data in p-Pb and Pb-Pb collisions cannot be described by an incoherent superposition of nucleon-nucleon collisions and pose a challenge to most of the event generators.
The average transverse momentum as a function of multiplicity of charged particles having transverse momentum in the range 0.15-10 GeV/c and |eta| < 0.3 produced from P-P collisions at a centre-of mass energy/nucleon of 0.9 TeV.
The average transverse momentum as a function of multiplicity of charged particles having transverse momentum in the range 0.15-10 GeV/c and |eta| < 0.3 produced from P-P collisions at a centre-of mass energy/nucleon of 2.76 TeV.
The average transverse momentum as a function of multiplicity of charged particles having transverse momentum in the range 0.15-10 GeV/c and |eta| < 0.3 produced from P-P collisions at a centre-of mass energy/nucleon of 7 TeV.
Angular correlations between unidentified charged trigger particles and various species of charged associated particles (unidentified particles, pions, kaons, protons and antiprotons) are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV in the transverse-momentum range $0.3 < p_{\rm T} < 4$ GeV/$c$. The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range $|\eta_{\rm lab}|<0.8$. Fourier coefficients are extracted from the long-range correlations projected onto the azimuthal angle difference and studied as a function of $p_{\rm T}$ and in intervals of event multiplicity. In high-multiplicity events, the second-order coefficient for protons, $v_2^p$, is observed to be smaller than that for pions, $v_2^\pi$, up to about $p_{\rm T} = 2$ GeV/$c$. To reduce correlations due to jets, the per-trigger yield measured in low-multiplicity events is subtracted from that in high-multiplicity events. A two-ridge structure is obtained for all particle species. The Fourier decomposition of this structure shows that the second-order coefficients for pions and kaons are similar. The $v_2^p$ is found to be smaller at low $p_{\rm T}$ and larger at higher $p_{\rm T}$ than $v_2^pi$, with a crossing occurring at about 2 GeV. This is qualitatively similar to the elliptic-flow pattern observed in heavy-ion collisions. A mass ordering effect at low transverse momenta is consistent with expectations from hydrodynamic model calculations assuming a collectively expanding system.
The Fourier coefficients V2(2PC,sub) extracted for all charged particles as a function of PT from the correlation in the 0-20% multiplicity class after subraction of the correlation from the 60-100% event class.
The Fourier coefficients V2(2PC,sub) extracted for charged pions as a function of PT from the correlation in the 0-20% multiplicity class after subraction of the correlation from the 60-100% event class.
The Fourier coefficients V2(2PC,sub) extracted for charged kaons as a function of PT from the correlation in the 0-20% multiplicity class after subraction of the correlation from the 60-100% event class.
In this Letter, comprehensive results on ${\rm\pi}^\pm$, K$^\pm$, K$^0_S$, p, $\rm\bar{p}$, $\rm \Lambda$ and $\rm \bar{\Lambda}$ production at mid-rapidity ($0 < y_{\rm cms} < 0.5$) in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, measured by the ALICE detector at the LHC, are reported. The transverse momentum distributions exhibit a hardening as a function of event multiplicity, which is stronger for heavier particles. This behavior is similar to what has been observed in pp and Pb-Pb collisions at the LHC. The measured $p_{\rm T}$ distributions are compared to results at lower energy and with predictions based on QCD-inspired and hydrodynamic models.
pT-differential invariant yield of charged pions in pPb collisions with centre-of-mass energy/nucleon=5.02 TeV.
pT-differential invariant yield of charged pions in pPb collisions with centre-of-mass energy/nucleon=5.02 TeV.
pT-differential invariant yield of charged pions in pPb collisions with centre-of-mass energy/nucleon=5.02 TeV.
In high-energy collisions, the spatio-temporal size of the particle production region can be measured using the Bose-Einstein correlations of identical bosons at low relative momentum. The source radii are typically extracted using two-pion correlations, and characterize the system at the last stage of interaction, called kinetic freeze-out. In low-multiplicity collisions, unlike in high-multiplicity collisions, two-pion correlations are substantially altered by background correlations, e.g. mini-jets. Such correlations can be suppressed using three-pion cumulant correlations. We present the first measurements of the size of the system at freeze-out extracted from three-pion cumulant correlations in pp, p-Pb and Pb-Pb collisions at the LHC with ALICE. At similar multiplicity, the invariant radii extracted in p-Pb collisions are found to be 5-15% larger than those in pp, while those in Pb-Pb are 35-55% larger than those in p-Pb. Our measurements disfavor models which incorporate substantially stronger collective expansion in p-Pb as compared to pp collisions at similar multiplicity.
Mixed charge C3 and c3 in pp collisions projected against 1 of a mixed-charge pair invariant relative momentum.
Same charge C3 and c3 in pp collisions projected against Q3.
Same charge C3 and c3 in p Pb collisions projected against Q3.
The transverse momentum ($p_{\mathrm T}$) distribution of primary charged particles is measured at midrapidity in minimum-bias p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC in the range $0.15<p_{\mathrm T}<50$ GeV/$c$. The spectra are compared to the expectation based on binary collision scaling of particle production in pp collisions, leading to a nuclear modification factor consistent with unity for $p_{\mathrm T}$ larger than 2 GeV/$c$, with a weak indication of a Cronin-like enhancement for $p_{\rm T}$ around 4 GeV/$c$. The measurement is compared to theoretical calculations and to data in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV.
Transverse momentum distributions of charged particles in minimum-bias (NSD) p-Pb collisions for different pseudorapidity ranges.
The histogram represents the reference spectrum (cross section scaled by the nuclear overlap function, T(pPb)) in inelastic pp collisions, determined in |eta(cms)| < 0.8.
The ratio of spectra in p-Pb at backward pseudorapidities to that at |eta(cms)| < 0.3.
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