Particle Production In Pp Collisions Research Articles

Mixed-species charge and baryon balance functions studies with PYTHIA

Mixed species charge and baryon balance functions are computed based on proton-proton (pp) collisions simulated with the PYTHIA8 model. Simulations are performed with selected values of the collision energy s and the Monash tune and the ropes and shoving modes of PYTHIA8 to explore whether such measurements provide useful new information and constraints on mechanisms of particle production in pp collisions. Charge balance functions are studied based on mixed pairs of pions, kaons, and protons, whereas baryon balance functions are computed for mixed low mass strange and nonstrange baryons. Both charge and baryon balance functions of mixed particle pairs feature shapes and amplitudes that sensitively depend on the particle considered owing largely to the particle production mechanisms implemented in PYTHIA. The evolution of balance functions integrals with the longitudinal width of the acceptance are presented and one finds that sums of such integrals for a given reference particle obey expected sum rules for both charge and baryon balance functions. Additionally, both types of balance functions are found to evolve in shape and amplitude with increasing collision energy s and the PYTHIA tunes considered. Published by the American Physical Society 2024

Statistical Thermal Model for Particle Production in pp Collisions at RHIC and LHC Energies

In this paper, an improved multi-source thermal model is used to analyze the transverse momentum spectra in pp collisions at high energies, ranging from sNN = 62.4 GeV to 7 TeV. Via a detailed comparison between the model results and experimental data at RHIC and LHC energies, the thermodynamic properties of particle production are decided. It is shown that the excitation factors of emission sources depend linearly on lnsNN in the framework. Based on the variation regularity of the source excitation factors, transverse momentum spectra are predicted in pp collisions at higher energies; potential future pp colliders operating at sNN = 33 and 100 TeV.

Charged particle production in pp collisions at s = 8, 7 and 2.76 TeV at the LHC-a case study

We analyze the charged-particle multiplicity distributions measured by the ALICE experiment, over a wide pseudorapidity range, for [Formula: see text] collisions at [Formula: see text], 7 and 2.76 TeV at the LHC. The analysis offers an understanding of particle production in high energy collisions in the purview of a new distribution, the shifted Gompertz distribution. Data are compared with the distribution and moments of the distributions are calculated. A modified version of the distribution is also proposed and used to improve the description of the data consisting of two different event classes: the inelastic and the nonsingle diffractive and their subsets in different windows of pseudorapidity, [Formula: see text]. The distribution used to analyze the data has a wide range of applicability to processes in different fields and complements the analysis done by the ALICE collaboration in terms of various LHC event generators and IP-Glasma calculations.

Simulation studies of R2(Δη,Δφ) and P2(Δη,Δφ) correlation functions in pp collisions with the PYTHIA and HERWIG models

We report studies of charge-independent (CI) and charge-dependent (CD) two-particle differential-number correlation functions, $\rm{R_{2}}(\Delta\eta, \Delta\varphi)$, and transverse momentum ($p_{\rm T}$) correlation functions, $\rm{P_{2}}(\Delta\eta, \Delta\varphi)$, of charged particles in $\sqrt{\textit{s}}$ = 2.76 TeV pp collisions with the PYTHIA and HERWIG models. Model predictions are presented for inclusive charged hadrons ($h^\pm$), as well as pions ($\pi^\pm$), kaons (K$^\pm$), and (anti-)protons ($\rm \bar{p}$/p) in the ranges $0.2 < \textit{p}_{\rm T} \le 2.0~\rm{GeV}/\textit{c}$, $2.0 < \textit{p}_{\rm T} \le 5.0~\rm{GeV}/\textit{c}$, and $5.0 < \textit{p}_{\rm T} \le 30.0~\rm{GeV}/\textit{c}$, with full azimuthal coverage in the range $|\eta|< 1.0$. We compare the model predictions for the strength and shape of the $\rm{R_{2}}$ and $\rm{P_{2}}$ correlators as these pertain to recent measurements by the ALICE collaboration. The $\rm{R_{2}}$ and $\rm{P_{2}}$ correlation functions estimated with PYTHIA and HERWIG exhibit qualitatively similar near-side and away-side correlation structures but feature important differences. Our analysis indicates that comparative studies of $\rm{R_{2}}$ and $\rm{P_{2}}$ correlation functions would provide valuable insight towards the understanding of particle production in pp collisions, and by extension, should also be useful in studies of heavy-ion collisions. Comparison of the $\Delta \eta$ dependence of $\rm{R_{2}}$ and $\rm{P_{2}}$ could contribute, in particular, to a better understanding and modeling of the angular ordering of particles produced by hadronization in jets, as well as a better description of jet fragmentation functions of identified species at low momentum fraction $(z)$.

Event-shape- and multiplicity-dependent identified particle production in pp collisions at 13 TeV with ALICE at the LHC

Multiplicity-dependent measurements of identified particle production led to the discovery of collective-like behavior in pp collisions at the LHC. Better understanding of the effects attributed to well-understood physics, like multiple hard scatterings, is required to establish whether this behaviour is truly collective in origin. Experimentally, those effects can be controlled using event shapes, like transverse spherocity, which allows the classification of pp collisions either as jetty or isotropic events. The transverse momentum (pT) spectra of light-flavor hadrons in pp collisions measured over a broad range provide important input to study particle production mechanisms in the soft and hard scattering regimes of the QCD. In this work, they are used to perform a comprehensive study as a function of the event multiplicity, collision energy, and event shapes. The proton-to-pion and kaon-to-pion particle ratios as a function of pT are also reported and the results compared to QCD-inspired models.

Prediction of the particle production in pp collisions with the MPD detector at NICA collider

The proton-proton collisions have been extensively used as a baseline reference for nucleus-nucleus collisions. In this work, Monte Carlo simulations of inelastic head-on pp interactions at $\sqrt s = 6 - 25\,{\rm{GeV}}$ were performed to study the possibilities of the Multi–Purpose Detector (MPD) to register data from small systems at the energy range of NICA. For that purpose the Monte Carlo models EPOS 1.99 and UrQMD 3.4 were used as event generators to analyse the charge particle yield from pp collisions in the framework of MpdRoot. The production of protons, pions and kaons from pp collisions was studied through their mean multiplicity, rapidity spectra and particle ratios as function of the collision energy. The yield of Λ hyperons was also estimated by means of pure Monte Carlo and the reconstruction of the simulated data in MPD. The comparison with recent data from NA61/SHINE experiment is presented.

Multiplicity Dependence of Strangeness and Charged Particle Production in Proton--Proton Collisions

In this contribution, the production rates and the transverse momentum distributions of strange hadrons are reported as a function of charged particle multiplicity. In this analysis, the data collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ALICE detector at the LHC are used. It is found that the production rate of $K_{S}^{0}$, $\Lambda$, $\Xi^{\pm}$, and $\Omega$ increases with multiplicity faster than that for charged particles. The higher the strangeness content of the hadron, the more pronounced is the increase. Moreover, the energy and multiplicity dependence of charged particle production in pp collisions are presented and the results are compared to predictions from Monte Carlo (MC) event generators. It turns out that the average multiplicity density increases steeply with center-of-mass energy for high multiplicity classes.

Strangeness Production in pp, p–Pb and Pb–Pb Collisions at the LHC Energies Measured with ALICE

The main goal of heavy-ion physics is to study the properties of the deconfined state of matter known as the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions. A systematic study of strangeness production is of fundamental importance for determining the thermal properties of the system created in such collisions. In the central barrel of the ALICE detector, K[Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] can be identified reconstructing their weak decay topology. It will be shown that the relative production (to pions) of strange particles follows a continuous increasing trend from low multiplicity pp to peripheral Pb–Pb collisions, above which a saturation is visible for central Pb–Pb collisions. This increasing trend is similar for pp and p–Pb collisions. Moreover, comparison of strange particle production in pp collisions at two different energies ([Formula: see text] = 7 TeV and 13 TeV) will be used to demonstrate that the observed trend in multiplicity is also energy independent.

Identified particle production in pp collisions at = 7 and 13 TeV measured with ALICE

Proton-proton (pp) collisions have been used extensively as a reference for the study of interactions of larger colliding systems at the LHC. Recent measurements performed in high-multiplicity pp and proton-lead (p-Pb) collisions have shown features that are reminiscent of those observed in lead-lead (Pb-Pb) collisions. In this context, the study of identified particle spectra and yields as a function of multiplicity is a key tool for the understanding of similarities and differences between small and large systems. We report on the production of pions, kaons, protons, , Λ, Ξ, Ω and K*0 as a function of multiplicity in pp collisions at = 7 TeV measured with the ALICE experiment. The work presented here represents the most comprehensive set of results on identified particle production in pp collisions at the LHC. Spectral shapes, studied both for individual particles and via particle ratios as a function of pT, exhibit an evolution with charged particle multiplicity that is similar to the one observed in larger systems. In addition, results on the production of light flavour hadrons in pp collisions at = 13 TeV, the highest centre-of-mass energy ever reached in the laboratory, are also presented and compared with previous, lower energy results.

Studies of particle production in pp collisions in the forward region at LHCb

The LHCb detector at the LHC has a pseudorapidity coverage (2<η<5) which allows it to perform particle production measurements in a kinematic region where QCD models have large uncertainties. Selected analyses on particle production measurements in pp collisions are summarised in these proceedings. The energy flow has been measured separately for different event classes allowing to probe multi-parton interactions at large η. The measured prompt hadron ratios are important for hadronisation models, while the p‾/p ratio is a good observable to test models of baryon number transport. Charm production has been studied to determine cross-sections and production ratios. All measurements are compared to a variety of theory predictions.

Transverse momentum dependence of inclusive primary charged-particle production in p–Pb collisions at $$\sqrt{s_\mathrm{{NN}}}=5.02~\text {TeV}$$ s NN = 5.02 TeV

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 $$p_\mathrm {T}$$ around 4 $$\mathrm {GeV}\!/c$$ . The measurement is compared to theoretical calculations and to data in Pb–Pb collisions at $$\sqrt{s_{\mathrm {NN}}}=2.76$$ TeV.

Mid-rapidity anti-baryon to baryon ratios in pp collisions at $\sqrt{s} = 0.9,\ 2.76\mbox{ and }7\mbox{ TeV}$ measured by ALICE

The ratios of yields of anti-baryons to baryons probes the mechanisms of baryon-number transport. Results for $\bar{\rm p}/{\rm p}$, $\bar{\rm \Lambda}/{\rm \Lambda}$, $\rm\bar{\Xi}$$^{+}/{\rm \Xi}^{-}$ and $\rm\bar{\Omega}$$^{+}/{\rm \Omega}^{-}$ in pp collisions at $\sqrt{s} = 0.9$, 2.76 and 7 TeV, measured with the ALICE detector at the LHC, are reported. Within the experimental uncertainties and ranges covered by our measurement, these ratios are independent of rapidity, transverse momentum and multiplicity for all measured energies. The results are compared to expectations from event generators, such as PYTHIA and HIJING-B, that are used to model the particle production in pp collisions. The energy dependence of $\bar{\rm p}/{\rm p}$, $\bar{\rm \Lambda}/{\rm \Lambda}$, $\rm\bar{\Xi}$$^{+}/{\rm \Xi^{-}}$ and $\rm\bar{\Omega}$$^{+}/{\rm \Omega^{-}}$, reaching values compatible with unity for $\sqrt{s} = 7$ TeV, complement the earlier $\bar{\rm p}/{\rm p}$ measurement of ALICE. These dependencies can be described by exchanges with the Regge-trajectory intercept of $\alpha_{\rm {J}} \approx 0.5$, which are suppressed with increasing rapidity interval ${\rm \Delta} y$. Any significant contribution of an exchange not suppressed at large ${\rm \Delta} y$ (reached at LHC energies) is disfavoured.

Measurements of Particle Production in pp Collisions in the Forward Region at the LHC

The phase space coverage of the LHCb detector allows a unique insight into the particle production in the forward region at the LHC. Due to its unique pseudorapidity range and to the possibility of extending the measurements to low transverse momenta, the LHCb data provide important input to the understanding of particle production in a kinematical range where QCD models have large uncertainties. Measurements of the production of charged particles and of the strange phi mesons are presented. In addition the ratio of (Lambda) over bar/Lambda is studied as a function of rapidity and transverse momentum for centre-of-mass energies root s = 0.9 TeV and root s = 7.0 TeV, probing baryon number transport from the beam. Baryon strangeness suppression is evaluated through the measurement of (Lambda) over bar /K-S(0). The LHCb results are compared with lower energy measurements, phenomenological models and Monte Carlo event generators.

Strange quark suppression and strange hadron production inppcollisions at energies available at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider

The parton and hadron cascade model PACIAE based on PYTHIA was utilized to systematically investigate the strange particle production in pp collisions at the RHIC and LHC energies. Taking the mechanism of reduction of the strange quark suppression into account the STAR and ALICE data of strange particle production in pp collisions are well reproduced. It turned out that the K/{\pi} ratio as a function of reaction energy in pp collisions shows slightly increasing from sqrt(s)=0.2 to 0.9 TeV and then turning to saturation.

Strange particle production in pp collisions at $ \sqrt {s} = 0.9 $ and 7 TeV

The spectra of strange hadrons are measured in proton-proton collisions, recorded by the CMS experiment at the CERN LHC, at centre-of-mass energies of 0.9 and 7 TeV. The \( {\text{K}}_{\text{S}}^0 \), Λ, and Ξ− particles and their antiparticles are reconstructed from their decay topologies and the production rates are measured as functions of rapidity and transverse momentum, p T. The results are compared to other experiments and to predictions of the Pythia Monte Carlo program. The p T distributions are found to differ substantially from the Pythia results and the production rates exceed the predictions by up to a factor of three.

Study of strange particle production in pp collisions with the ALICE detector

ALICE is well suited for strange particle production studies since it has very good reconstruction capabilities in the low transverse momentum (pt) region and it also allows the identification to be extended up to quite high pt. Charged strange mesons (K+, K−) are reconstructed via energy loss measurements whereas neutral strange mesons (K0s) and strange hyperons (Λ, Ξ, Ω) are identified via vertex reconstruction. All these particles carry important information: firstly, the measurement of production yields and the particle ratio within the statistical models can help to understand the medium created, and secondly the dynamics at intermediate pt investigated via the baryon over meson ratio (Λ/K0s) allows a better understanding of the hadronization mechanisms and of the underlying event processes. We present these two aspects of the strange particle analysis in pp collisions using simulated data.

COLORED SCALAR PARTICLES PRODUCTION IN pp-COLLISIONS AND POSSIBLE MASS LIMITS FOR SCALAR GLUONS FROM FUTURE LHC DATA

Cross sections of the colored scalar particle production in pp-collisions are calculated and differential and total cross sections of the corresponding parton subprocesses are obtained. The total cross section of scalar gluon production in pp-collisions at the LHC is estimated and the dominant decays of scalar gluons are discussed. The production cross section of scalar gluons F with masses mF ≲ 1300 GeV is shown to be sufficient for the effective production of these particles at the LHC.

Neutral strange-particle production in pp collisions at 6.92 GeV/c

Neutral strange particle production in pp collisions at 6.92 GeV/c has been studied in the 80 in. HBC at BNL. Partial crosssections for the different channels are given. No evidence for hyperon-nucleon resonances has been observed. Strong production ofN 3/2 * (1236) and Y 1 * (1385) has been seen in the four- and five-body final states, which has been analysed in terms of a one-pion-exchange mechanism.