We report measurements of the third harmonic coefficient of the azimuthal anisotropy, v_3, known as triangular flow. The analysis is for charged particles in Au+Au collisions at sqrtsNN = 200 GeV, based on data from the STAR experiment at the Relativistic Heavy Ion Collider. Two-particle correlations as a function of their pseudorapidity separation are fit with narrow and wide Gaussians. Measurements of triangular flow are extracted from the wide Gaussian, from two-particle cumulants with a pseudorapidity gap, and also from event plane analysis methods with a large pseudorapidity gap between the particles and the event plane. These results are reported as a function of transverse momentum and centrality. A large dependence on the pseudorapidity gap is found. Results are compared with other experiments and model calculations.
Gaussian Width (W) as a function of transverse momentum for most central (0-5%) and mid-central (30-40%) Au+Au collision at sqrt(snn)=200 GEV.
Amplitude (A) as a function of transverse momentum for most central (0-5%) and mid-central (30-40%) Au+Au collision at sqrt(snn)=200 GEV.
Gaussian Width (W) as a function of centrality for Like Sign (LS) and Charge Independent (CI) particles for Au+Au collision at sqrt(snn)=200 GEV.
Measurements of the elliptic flow, $v_{2}$, of identified hadrons ($\pi^{\pm}$, $K^{\pm}$, $K_{s}^{0}$, $p$, $\bar{p}$, $\phi$, $\Lambda$, $\bar{\Lambda}$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$, $\bar{\Omega}^{+}$) in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV are presented. The measurements were done at mid-rapidity using the Time Projection Chamber and the Time-of-Flight detectors of the STAR experiment during the Beam Energy Scan program at RHIC. A significant difference in the $v_{2}$ values for particles and the corresponding anti-particles was observed at all transverse momenta for the first time. The difference increases with decreasing center-of-mass energy, $\sqrt{s_{NN}}$ (or increasing baryon chemical potential, $\mu_{B}$) and is larger for the baryons as compared to the mesons. This implies that particles and anti-particles are no longer consistent with the universal number-of-constituent quark (NCQ) scaling of $v_{2}$ that was observed at $\sqrt{s_{NN}}=$ 200 GeV. However, for the group of particles NCQ scaling at $(m_{T}-m_{0})/n_{q}>$ 0.4 GeV/$c^{2}$ is not violated within $\pm$10%. The $v_{2}$ values for $\phi$ mesons at 7.7 and 11.5 GeV are approximately two standard deviations from the trend defined by the other hadrons at the highest measured $p_{T}$ values.
The elliptic flow,v_2, as a function of the transverse momentum,p_T, from 0–80% central Au+Au collisions for various particle species and energies.
The elliptic flow,v_2, as a function of the transverse momentum,p_T, from 0–80% central Au+Au collisions for various particle species and energies.
The elliptic flow,v_2, as a function of the transverse momentum,p_T, from 0–80% central Au+Au collisions for various particle species and energies.
The ALICE collaboration at the CERN Large Hadron Collider reports the first measurement of the inclusive differential jet cross section at mid-rapidity in pp collisions at $\sqrt{s} = 2.76$ TeV, with integrated luminosity of 13.6 nb$^{-1}$. Jets are measured over the transverse momentum range 20 to 125 GeV/c and are corrected to the particle level. Calculations based on Next-to-Leading Order perturbative QCD are in good agreement with the measurements. The ratio of inclusive jet cross sections for jet radii $R = 0.2$ and $R = 0.4$ is reported, and is also well reproduced by a Next-to-Leading Order perturbative QCD calculation when hadronization effects are included.
Inclusive differential jet cross section for R=0.2 and R=0.4.
Ratio of the inclusive differential jet cross section for R=0.2 and R=0.4.
In high-energy heavy-ion collisions, the correlations between the emitted particles can be used as a probe to gain insight into the charge creation mechanisms. In this Letter, we report the first results of such studies using the electric charge balance function in the relative pseudorapidity ($\Delta\eta$) and azimuthal angle ($\Delta\varphi$) in Pb--Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV with the ALICE detector at the Large Hadron Collider. The width of the balance function decreases with growing centrality (i.e. for more central collisions) in both projections. This centrality dependence is not reproduced by HIJING, while AMPT, a model which incorporates strings and parton rescattering, exhibits qualitative agreement with the measured correlations in $\Delta\varphi$ but fails to describe the correlations in $\Delta\eta$. A thermal blast-wave model incorporating local charge conservation and tuned to describe the $p_{\rm T}$ spectra and v$_2$ measurements reported by ALICE, is used to fit the centrality dependence of the width of the balance function and to extract the average separation of balancing charges at freeze-out. The comparison of our results with measurements at lower energies reveals an ordering with $\sqrt{s_{\rm NN}}$: the balance functions become narrower with increasing energy for all centralities. This is consistent with the effect of larger radial flow at the LHC energies but also with the late stage creation scenario of balancing charges. However, the relative decrease of the balance function widths in $\Delta\eta$ and $\Delta\varphi$ with centrality from the highest SPS to the LHC energy exhibits only small differences. This observation cannot be interpreted solely within the framework where the majority of the charge is produced at a later stage in the evolution of the heavy--ion collision.
The Balance Function as a function of the relative pseudorapidity of two charged particles for the centrality class 0-5%. Also shown in the second column is the result from the mixed data set.
The Balance Function as a function of the relative pseudorapidity of two charged particles for the centrality class 30-40%.
The Balance Function as a function of the relative pseudorapidity of two charged particles for the centrality class 70-80%.
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.
The measurement of J/{psi} azimuthal anisotropy is presented as a function of transverse momentum for different centralities in Au+Au collisions at {sqrt{s_{NN}}} = 200 GeV. The measured J/{psi} elliptic flow is consistent with zero within errors for transverse momentum between 2 and 10 GeV/c. Our measurement suggests that J/{psi} with relatively large transverse momentum are not dominantly produced by coalescence from thermalized charm quarks, when comparing to model calculations.
J/Psi azimuthal anisotropy v2 vs pT measured via the dielectron channel in 0-10%, 10-40%, and 40-80% central Au+Au collisions at 200 GeV. The brackets represent systematic errors. The boxes show the estimated maximum possible range of v2 if the nonflow influence is corrected. The mean pT in each bin for v2 calculation is drawn, but is shifted a little for some centralities so that all points can be seen clearly.
J/Psi azimuthal anisotropy v2 vs pT measured via the dielectron channel in 0-80% central Au+Au collisions at 200 GeV. The brackets represent systematic errors. The boxes show the estimated maximum possible range of v2 if the nonflow influence is corrected.
Jet-medium interactions are studied via a multi-hadron correlation technique (called "2+1"), where a pair of back-to-back hadron triggers with large transverse momentum is used as a proxy for a di-jet. This work extends the previous analysis for nearly-symmetric trigger pairs with the highest momentum threshold of trigger hadron of 5 GeV/$c$ with the new calorimeter-based triggers with energy thresholds of up to 10 GeV and above. The distributions of associated hadrons are studied in terms of correlation shapes and per-trigger yields on each trigger side. In contrast with di-hadron correlation results with single triggers, the associated hadron distributions for back-to-back triggers from central Au+Au data at $\sqrt{s_{NN}}$=200 GeV show no strong modifications compared to d+Au data at the same energy. An imbalance in the total transverse momentum between hadrons attributed to the near-side and away-side of jet-like peaks is observed. The relative imbalance in the Au+Au measurement with respect to d+Au reference is found to increase with the asymmetry of the trigger pair, consistent with expectation from medium-induced energy loss effects. In addition, this relative total transverse momentum imbalance is found to decrease for softer associated hadrons. Such evolution indicates the energy missing at higher associated momenta is converted into softer hadrons.
Projections of 2-D correlation functions on $\Delta \phi$ (a) (with $|\Delta \eta|$ < 1.0) and $\Delta \eta$ (b) (with $|\Delta \phi|$ < 0.7) for the hadrons associated with their respective triggers (T1 for near-side, T2 for away–side) are shown for d+Au (circles) and central 0-20% Au+Au (squares).
Projections of 2-D correlation functions on $\Delta \phi$ (a) (with $|\Delta \eta|$ < 1.0) and $\Delta \eta$ (b) (with $|\Delta \phi|$ < 0.7) for the hadrons associated with their respective triggers (T1 for near-side, T2 for away–side) are shown for d+Au (circles) and central 0-20% Au+Au (squares).
Projections of 2-D correlation functions on $\Delta \phi$ (a) (with $|\Delta \eta|$ < 1.0) and $\Delta \eta$ (b) (with $|\Delta \phi|$ < 0.7) for the hadrons associated with their respective triggers (T1 for near-side, T2 for away–side) are shown for d+Au (circles) and central 0-20% Au+Au (squares).
The jet fragmentation function is measured with direct photon-hadron correlations in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. The p_T of the photon is an excellent approximation to the initial p_T of the jet and the ratio z_T=p_T^h/p_T^\gamma is used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon-hadron yields in Au+Au collisions while a photon isolation cut is applied in p+p. I_ AA, the ratio of jet fragment yield in Au+Au to that in p+p, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high z_T. The fragment yield at low z_T is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.
Direct photon-hadron pair per-trigger yields vs Delta-phi (Au+Au and p+p)
Integrated per-trigger yields and I_AA vs xi
Integrated per-trigger yields and I_AA vs xi
The three Upsilon states, Upsilon(1S+2S+3S), are measured in d+Au and p+p collisions at sqrt(s_NN)=200 GeV and rapidities 1.2<|y|<2.2 by the PHENIX experiment at the Relativistic Heavy-Ion Collider. Cross sections for the inclusive Upsilon(1S+2S+3S) production are obtained. The inclusive yields per binary collision for d+Au collisions relative to those in p+p collisions (R_dAu) are found to be 0.62 +/- 0.26 (stat) +/- 0.13 (syst) in the gold-going direction and 0.91 +/- 0.33 (stat) +/- 0.16 (syst) in the deuteron-going direction. The measured results are compared to a nuclear-shadowing model, EPS09 [JHEP 04, 065 (2009)], combined with a final-state breakup cross section, sigma_br, and compared to lower energy p+A results. We also compare the results to the PHENIX J/psi results [Phys. Rev. Lett. 107, 142301 (2011)]. The rapidity dependence of the observed Upsilon suppression is consistent with lower energy p+A measurements.
$\Upsilon$ invariant yields and cross sections of $p$+$p$ and $d$+Au collisions.
The $p_{\rm T}$-differential inclusive production cross section of the prompt charm-strange meson $\rm D_s^+$ in the rapidity range $|y|<0.5$ was measured in proton-proton collisions at $\sqrt{s}=7$ TeV at the LHC using the ALICE detector. The analysis was performed on a data sample of $2.98 \times 10^8$ events collected with a minimum-bias trigger. The corresponding integrated luminosity is $L_{\rm int}=4.8$/nb. Reconstructing the decay ${\rm D_s^{+}\to \phi\pi^+}$, with $\phi\to {\rm K}^-{\rm K}^+$, and its charge conjugate, about 480 ${\rm D_s^{\pm}}$ mesons were counted, after selection cuts, in the transverse momentum range $2<p_{\rm T}<12$ Gev/$c$. The results are compared with predictions from models based on perturbative QCD. The ratios of the cross sections of four D meson species (namely ${\rm D^0}$, ${\rm D^+}$, ${\rm D^{*+}}$ and ${\rm D_s^+}$) were determined both as a function of $p_{\rm T}$ and integrated over $p_{\rm T}$ after extrapolating to full $p_{\rm T}$ range, together with the strangeness suppression factor in charm fragmentation. The obtained values are found to be compatible within uncertainties with those measured by other experiments in $\rm e^+e^-$, ep and pp interactions at various centre-of-mass energies.
pT-differential inclusive cross section in |y| < 0.5 for prompt D_s^+ meson production in pp collisions at sqrt(s) = 7 TeV.
pT-integrated inclusive cross section in |y| < 0.5 for prompt D_s^+ meson production in pp collisions at sqrt(s) = 7 TeV. The latter three systematic uncertainties arise from extrapolating the visible cross section to the full pT range, luminosity, and the branching ratio, respectively.
Ratio of D^+ to D^0 meson production cross sections in |y| < 0.5 as a function of pT.
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