Identified charged particle spectra of $\pi^{\pm}$, $K^{\pm}$, $p$ and $\pbar$ at mid-rapidity ($|y|<0.1$) measured by the $\dedx$ method in the STAR-TPC are reported for $pp$ and d+Au collisions at $\snn = 200$ GeV and for Au+Au collisions at 62.4 GeV, 130 GeV, and 200 GeV. ... [Shortened for arXiv list. Full abstract in manuscript.]
Charged-particle spectra associated with direct photon ($\gamma_{dir} $) and $\pi^0$ are measured in $p$+$p$ and Au+Au collisions at center-of-mass energy $\sqrt{s_{_{NN}}}=200$ GeV with the STAR detector at RHIC. A hower-shape analysis is used to partially discriminate between $\gamma_{dir}$ and $\pi^0$. Assuming no associated charged particles in the $\gamma_{dir}$ direction (near side) and small contribution from fragmentation photons ($\gamma_{frag}$), the associated charged-particle yields opposite to $\gamma_{dir}$ (away side) are extracted. At mid-rapidity ($|\eta|<0.9$) in central Au+Au collisions, charged-particle yields associated with $\gamma_{dir}$ and $\pi^0$ at high transverse momentum ($8< p_{T}^{trig}<16$ GeV/$c$) are suppressed by a factor of 3-5 compared with $p$ + $p$ collisions. The observed suppression of the associated charged particles, in the kinematic range $|\eta|<1$ and $3< p_{T}^{assoc} < 16$ GeV/$c$, is similar for $\gamma_{dir}$ and $\pi^0$, and independent of the $\gamma_{dir}$ energy within uncertainties. These measurements indicate that the parton energy loss, in the covered kinematic range, is insensitive to the parton path length.
The $z_{T}$ dependence of $\pi^{0}-h^{\pm}$ near side and away-side associated particle yields. The errors denoted 'syst' are systematic errors correlated in $z_{T}$. The errors denoted 'syst uncorr' are point-to-point systematic errors.
The $z_{T}$ dependence of away-side associated-particle yields for $\pi^{0}-h^{\pm}$ triggers and $\gamma_{dir}$ triggers. The errors denoted 'syst' are systematic errors correlated in $z_{T}$. The errors denoted 'syst uncorr' are point-to-point systematic errors.
The $z_{T}$ dependence $I_{AA}$ for $\pi^{0}-h^{\pm}$ triggers and $\gamma_{dir}$ triggers. The errors denoted 'syst' are systematic errors correlated in $z_{T}$. The errors denoted 'syst uncorr' are point-to-point systematic errors.
Measurements of the differential cross-section and the transverse single-spin asymmetry, A_N, vs. x_F for pi0 and eta mesons are reported for 0.4 < x_F < 0.75 at an average pseudorapidity of 3.68. A data sample of approximately 6.3 pb^{-1} was analyzed, which was recorded during p+p collisions at sqrt{s} = 200 GeV by the STAR experiment at RHIC. The average transverse beam polarization was 56%. The cross-section for pi0 is consistent with a perturbative QCD prediction, and the eta/pi0 cross-section ratio agrees with previous mid-rapidity measurements. For 0.55 < x_F < 0.75, A_N for eta (0.210 +- 0.056) is 2.2 standard deviations larger than A_N for pi0 (0.081 +- 0.016).
Differential production cross-sections for $\pi^0$ and $\eta$ at average pseudorapidity of 3.68. Also shown are the previously published STAR results for similar kinematics [21] and a NLO pQCD calculation of the π0 cross-section [32]. The error band represents the uncertainty in the calculation due to scale variations.
The $\eta$ to $\pi^0$ cross-section ratio is shown in the bottom panel. The error bars indicate the total statistical and systematic uncertainties.
We report measurements of charmed-hadron ($D^{0}$, $D^{*}$) production cross sections at mid-rapidity in $p$ + $p$ collisions at a center-of-mass energy of 200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the hadronic decays $D^{0}\rightarrow K^{-}\pi^{+}$, $D^{*+}\rightarrow D^{0}\pi^{+}\rightarrow K^{-}\pi^{+}\pi^{+}$ and their charge conjugates, covering the $p_T$ range of 0.6$-$2.0 GeV/$c$ and 2.0$-$6.0 GeV/$c$ for $D^{0}$ and $D^{*+}$, respectively. From this analysis, the charm-pair production cross section at mid-rapidity is $d\sigma/dy|_{y=0}^{c\bar{c}}$ = 170 $\pm$ 45 (stat.) $^{+38}_{-59}$ (sys.) $\mu$b. The extracted charm-pair cross section is compared to perturbative QCD calculations. The transverse momentum differential cross section is found to be consistent with the upper bound of a Fixed-Order Next-to-Leading Logarithm calculation.
$c\bar{c}$ production cross section as inferred from D$^0$ and D$^\star$ production in p+p collisions at $\sqrt{s} = 200$ GeV at $|\eta| < 1$ compared with FONLL calculations. The D$^0$ and D$^\star$ data points were divided by the charm quark fragmentation ratios 0.565 ($c \rightarrow$ D$^0$) and 0.224 ($c \rightarrow$ D$^{\star +}$) [34], respectively, to convert to the $c\bar{c}$ production cross section.
We present the first measurements of femtoscopic correlations between the K$^0_{\rm S}$ and K$^{\rm \pm}$ particles in pp collisions at $\sqrt{s}=7$ TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding solely via the $a_0(980)$ resonance. The extracted kaon source radius and correlation strength parameters for K$^0_{\rm S}$K$^{\rm -}$ are found to be equal within the experimental uncertainties to those for K$^0_{\rm S}$K$^{\rm +}$. Results of the present study are compared with those from identical-kaon femtoscopic studies also performed with pp collisions at $\sqrt{s}=7$ TeV by ALICE and with a K$^0_{\rm S}$K$^{\rm \pm}$ measurement in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. Combined with the Pb-Pb results, our pp analysis is found to be compatible with the interpretation of the $a_0(980)$ having a tetraquark structure instead of that of a diquark.
Raw K0s K+ correlation function for all kT
Raw K0s K+ correlation function for kT < 0.85 GeV/c
Raw K0s K+ correlation function for kT > 0.85 GeV/c
A comprehensive survey of event-by-event fluctuations of charged hadron multiplicity in relativistic heavy ions is presented. The survey covers Au+Au collisions at sqrt(s_NN) = 62.4 and 200 GeV, and Cu+Cu collisions sqrt(s_NN) = 22.5, 62.4, and 200 GeV. Fluctuations are measured as a function of collision centrality, transverse momentum range, and charge sign. After correcting for non-dynamical fluctuations due to fluctuations in the collision geometry within a centrality bin, the remaining dynamical fluctuations expressed as the variance normalized by the mean tend to decrease with increasing centrality. The dynamical fluctuations are consistent with or below the expectation from a superposition of participant nucleon-nucleon collisions based upon p+p data, indicating that this dataset does not exhibit evidence of critical behavior in terms of the compressibility of the system. An analysis of Negative Binomial Distribution fits to the multiplicity distributions demonstrates that the heavy ion data exhibit weak clustering properties.
The mean from the NBD fit as a function of $N_{part}$ for 200 GeV Au+Au collisions over the range 0.2 < $p_T$ < 2.0 GeV/$c$.
The mean from the NBD fit as a function of $N_{part}$ for 62.4 GeV Au+Au collisions over the range 0.2 < $p_T$ < 2.0 GeV/$c$.
We present the first measurement of midrapidity vector meson φ production in Au+Au collisions at RHIC (sNN=130 GeV) from the STAR detector. For the 11% highest multiplicity collisions, the slope parameter from an exponential fit to the transverse mass distribution is T=379±50(stat)±45(syst) MeV, the yield dN/dy=5.73±0.37(stat)±0.69(syst) per event, and the ratio Nφ/Nh− is found to be 0.021±0.001(stat)±0.004(syst). The measured ratio Nφ/Nh− and T for the φ meson at midrapidity do not change for the selected multiplicity bins.
Slope parameter T, dN/y, $N_\phi/N_h^-$. Systematic uncertainties on T are 12%, on dN/dy are 12%, and on $N_{\phi}/N_{h^-}$ are 22%.
This paper presents several measurements of total production cross sections and total inelastic cross sections for the following reactions: $\pi^{+}$+C, $\pi^{+}$+Al, $K^{+}$+C, $K^{+}$+Al at 60 GeV/c, $\pi^{+}$+C and $\pi^{+}$+Al at 31 GeV/c . The measurements were made using the NA61/SHINE spectrometer at the CERN SPS. Comparisons with previous measurements are given and good agreement is seen. These interaction cross sections measurements are a key ingredient for neutrino flux prediction from the reinteractions of secondary hadrons in current and future accelerator-based long-baseline neutrino experiments.
Results of production cross section measurements on $\pi^+$ and $K^+$ beams. Measured channeles are $\pi^+$+C, $\pi^+$+Al, $K^+$+C, and $K^+$+Al at 60 GeV/c and $\pi^+$+C and $\pi^+$+Al at 31 GeV/c.
This paper presents measurements of production cross sections and inelastic cross sections for the following reactions: 60 GeV/$c$ protons with C, Be, Al targets and 120 GeV/$c$ protons with C and Be targets. The analysis was performed using the NA61/SHINE spectrometer at the CERN SPS. First measurements were obtained using protons at 120 GeV/$c$, while the results for protons at 60 GeV/$c$ were compared with previously published measurements. These interaction cross section measurements are critical inputs for neutrino flux prediction in current and future accelerator-based long-baseline neutrino experiments.
Results of production cross section measurements on proton beams. Measured channeles are p+C/Be/Al at 60 GeV and p+C/Be at 120 GeV.
We report first measurements of $e^{+}e^{-}$ pair production in the mass region 0.4 $
The centrality dependence of e+e− invariant mass spectra within the STAR acceptance from Au+Au collisions and U+U collisions for pair pT < 0.15 GeV/c. The vertical bars on data points depict the statistical uncertainties, while the systematic uncertainties are shown as gray boxes. The hadronic cocktail yields from U+U collisions are ∼5%–12% higher than those from Au+Au collisions in given centrality bins; thus only cocktails for Au+Au collisions are shown here as solid lines, with shaded bands representing the systematic uncertainties for clarity.
The centrality dependence of e+e− invariant mass spectra within the STAR acceptance from Au+Au collisions and U+U collisions for pair pT < 0.15 GeV/c. The vertical bars on data points depict the statistical uncertainties, while the systematic uncertainties are shown as gray boxes. The hadronic cocktail yields from U+U collisions are ∼5%–12% higher than those from Au+Au collisions in given centrality bins; thus only cocktails for Au+Au collisions are shown here as solid lines, with shaded bands representing the systematic uncertainties for clarity.
The centrality dependence of e+e− invariant mass spectra within the STAR acceptance from Au+Au collisions and U+U collisions for pair pT < 0.15 GeV/c. The vertical bars on data points depict the statistical uncertainties, while the systematic uncertainties are shown as gray boxes. The hadronic cocktail yields from U+U collisions are ∼5%–12% higher than those from Au+Au collisions in given centrality bins; thus only cocktails for Au+Au collisions are shown here as solid lines, with shaded bands representing the systematic uncertainties for clarity.
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