π+p, K+p, and pp interactions at 100 GeV are studied using the Fermilab hybrid 30-inch bubble chamber with associated downstream multiparticle spectrometer and an unseparated tagged positive beam. Topological cross sections and charged-particle-multiplicity moments are presented and good agreement is found with Koba-Nielsen-Olesen scaling. The charged-multiplicity second moment, f2cc, and the second moment of produced (+ -) pairs, f2−−, are presented both with and without the diffractive-dissociation events, and are discussed in terms of the two-component model invoked to explain pp multiplicity distributions above 100 GeV. Single-particle inclusive distributions are presented and studied in terms of the Regge-Mueller forms of approach to scaling at asymptotic energies. Pomeron factorization is found to hold in the target-proton-associated backward center-of-mass hemisphere for inclusive particle production by incident π+, K+, and protons.
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We present high-statistics results on the reactions a+p→c+X where a and c can be any of π±, K±, p, or p¯. The data were taken at 100 and 175 GeV/c incident momenta using the Fermilab Single-Arm Spectrometer operated over the kinematic range 0.2<x<1.0 and pt<~1.0 GeV/c. Investigating the x dependence of the data, we find agreement with a quark-parton picture, namely the cross sections have a power-law behavior in 1−x independent of pbeam and pt.
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An experiment using the Fermilab Single Arm Spectrometer (SAS) facility and an associated nonmagnetic vertex detector studied the reactions a+p→c+X, where a and c were π±, K±, p, or p¯. Extensive measurements were made at 100 and 175 GeV/c beam momenta with the outgoing hadrons detected in the SAS covering a kinematic range 0.12<x<1.0 and pT<1.25 GeV/c. Additional data covering a more restricted range in x were also gathered at 70 GeV/c incident momentum. In this high-statistics experiment, the identification of both the incoming and outgoing charged hadrons were made with a total of eight Čerenkov counters. New and extensive single-particle inclusive data for charged-particle production in low-pT hadronic fragmentation are presented. The average associated charged-particle multiplicity and pseudorapidity distributions are also given.
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We present the transverse momentum (pT) spectra for identified charged pions, protons and anti-protons from p+p and d+Au collisions at \sqrts_NN = 200 GeV. The spectra are measured around midrapidity (|y| < 0.5) over the range of 0.3 < pT < 10 GeV/c with particle identification from the ionization energy loss and its relativistic rise in the Time Projection Chamber and Time-of-Flight in STAR. The charged pion and proton+anti-proton spectra at high pT in p+p and d+Au collisions are in good agreement with a phenomenological model (EPOS) and with the next-to-leading order perturbative quantum chromodynamic (NLO pQCD) calculations with a specific fragmentation scheme and factorization scale. We found that all proton, anti-proton and charged pion spectra in p+p collisions follow xT-scalings for the momentum range where particle production is dominated by hard processes (pT > 2 GeV/c). The nuclear modification factor around midrapidity are found to be greater than unity for charged pions and to be even larger for protons at 2 < pT < 5 GeV/c.
Transverse momentum distribution for $\pi^+$ production in d+Au minbias events in the mid rapidity region, $|y|<0.5$.
Transverse momentum distribution for $\pi^+$ production in p+p NSD events in the mid rapidity region, $|y|<0.5$.
Transverse momentum distribution for $\pi^+$ production in d+Au collisions with centrality 0-20% in the mid rapidity region, $|y|<0.5$.
Transverse momentum distributions and yields for $\pi^{\pm}$, $K^{\pm}$, $p$ and $\bar{p}$ in $p+p$ collisions at $\sqrt{s}$=200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). These data provide important baseline spectra for comparisons with identified particle spectra in heavy ion collisions at RHIC. We present the inverse slope parameter $T_{\rm inv}$, mean transverse momentum $<p_T>$ and yield per unit rapidity $dN/dy$ at each energy, and compare them to other measurements at different $\sqrt{s}$ in $p+p$ and $p+\bar{p}$ collisions. We also present the scaling properties such as $m_T$ scaling, $x_T$ scaling on the $p_T$ spectra between different energies. To discuss the mechanism of the particle production in $p+p$ collisions, the measured spectra are compared to next-to-leading-order or next-to-leading-logarithmic perturbative quantum chromodynamics calculations.
Invariant cross sections for inclusive PI+ and PI- production in P P collisions at a centre-of-mass energy of 200 GeV. There is an additional normalization uncertainty of 9.7 PCT.
Invariant cross sections for inclusive K+ and K- production in P P collisions at a centre-of-mass energy of 200 GeV. There is an additional normalization uncertainty of 9.7 PCT.
Invariant cross sections for inclusive P and PBAR production in P P collisions at a centre-of-mass energy of 200 GeV with feed-down weak decay corrections NOT applied. There is an additional normalization uncertainty of 9.7 PCT.
Spectra of identified charged hadrons are measured in pp collisions at the LHC for sqrt(s) = 0.9, 2.76, and 7 TeV. Charged pions, kaons, and protons in the transverse-momentum range pt approximately 0.1-1.7 GeV and for rapidities abs(y) < 1 are identified via their energy loss in the CMS silicon tracker. The average pt increases rapidly with the mass of the hadron and the event charged-particle multiplicity, independently of the center-of-mass energy. The fully corrected pt spectra and integrated yields are compared to various tunes of the PYTHIA6 and PYTHIA8 event generators.
Measured transverse momentum distributions of identified charged hadrons (PI+, K+ and P) and at a centre-of-mass energy of 900 GeV.
Measured transverse momentum distributions of identified charged hadrons (PI-, K- and PBAR) and at a centre-of-mass energy of 900 GeV.
Measured transverse momentum distributions of identified charged hadrons (PI+, K+ and P) and at a centre-of-mass energy of 2760 GeV.
Transverse momentum spectra of $\pi^{\pm}$, $\rm K^{\pm}$ and p($\bar{\rm p}$) up to $p_{\rm T}$ = 20 GeV/$c$ at mid-rapidity in pp and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=$ 2.76 TeV have been measured using the ALICE detector at the Large Hadron Collider. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at $p_{\rm T} \approx 3 GeV/c$ in central Pb-Pb collisions. Below the peak, $p_{\rm T}$ < 3 GeV/$c$, both ratios are in good agreement with hydrodynamical calculations, suggesting that the peak itself is dominantly the result of radial flow rather than anomalous hadronization processes. For $p_{\rm T}$ > 10 GeV/$c$ particle ratios in pp and Pb-Pb collisions are in agreement and the nuclear modification factors for $\pi^{\pm}$, $\rm K^{\pm}$ and $\rm p$($\bar{\rm p}$) indicate that, within the systematic and statistical uncertainties, the suppression is the same. This suggests that the chemical composition of leading particles from jets in the medium is similar to that of vacuum jets.
Invariant yields of identified pions in central and peripheral Pb-Pb collisions, together with the unscaled pp reference yields.
Invariant yields of identified kaons in central and peripheral Pb-Pb collisions, together with the unscaled pp reference yields.
Invariant yields of identified protons in central and peripheral Pb-Pb collisions, together with the unscaled pp reference yields.
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.
We present the midrapidity charged pion invariant cross sections and the ratio of $\pi^-$-to-$\pi^+$ production ($5<p_T<13$ GeV/$c$), together with the double-helicity asymmetries ($5<p_T<12$ GeV/$c$) in polarized $p$$+$$p$ collisions at $\sqrt{s} = 200$ GeV. The cross section measurements are consistent with perturbative calculations in quantum chromodynamics within large uncertainties in the calculation due to the choice of factorization, renormalization, and fragmentation scales. However, the theoretical calculation of the ratio of $\pi^-$-to-$\pi^+$ production when considering these scale uncertainties overestimates the measured value, suggesting further investigation of the uncertainties on the charge-separated pion fragmentation functions is needed. Due to cancellations of uncertainties in the charge ratio, direct inclusion of these ratio data in future parameterizations should improve constraints on the flavor dependence of quark fragmentation functions to pions. By measuring charge-separated pion asymmetries, one can gain sensitivity to the sign of $\Delta G$ through the opposite sign of the up and down quark helicity distributions in conjunction with preferential fragmentation of positive pions from up quarks and negative pions from down quarks. The double-helicity asymmetries presented are sensitive to the gluon helicity distribution over an $x$ range of $\sim$0.03--0.16.
Invariant cross section for $\pi^+$ and $\pi^-$ hadrons, as well as the statistical and systematic uncertainties. In addition, there is an absolute scale uncertainty of 9.6$\%$.
Double-helicity asymmetries and statistical uncertainties for $\pi^+$ and $\pi^-$ hadrons. The primary systematic uncertainties, which are fully correlated between points, are $1.4\times10^{-3}$ from relative luminosity and a $^{+7.0\%}_{-7.7\%}$ scaling uncertainty from beam polarization.
Ratio of charged pion cross section, as shown in Fig.6.
The measurement of primary $\pi^{\pm}$, K$^{\pm}$, p and $\overline{p}$ production at mid-rapidity ($|y| <$ 0.5) in proton-proton collisions at $\sqrt{s} = 7$ TeV performed with ALICE (A Large Ion Collider Experiment) at the Large Hadron Collider (LHC) is reported. Particle identification is performed using the specific ionization energy loss and time-of-flight information, the ring-imaging Cherenkov technique and the kink-topology identification of weak decays of charged kaons. Transverse momentum spectra are measured from 0.1 up to 3 GeV/$c$ for pions, from 0.2 up to 6 GeV/$c$ for kaons and from 0.3 up to 6 GeV/$c$ for protons. The measured spectra and particle ratios are compared with QCD-inspired models, tuned to reproduce also the earlier measurements performed at the LHC. Furthermore, the integrated particle yields and ratios as well as the average transverse momenta are compared with results at lower collision energies.
Combined transverse momentum spectra of PI, K and P, sum of particles and antiparticles, measured at mid-rapidity in pp collisions at SQRT(S) = 7 TeV normalized to the number of inelastic collisions. Statistical and systematic uncertainties are reported. The uncertainty due to the normalization to inelastic collisions (+7-4 %) is not included.
Kaon/Pion ratio in pp collisions at SQRT(S) = 7 TeV.
Proton/Pion ratio in pp collisions at SQRT(S) = 7 TeV.
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