Meson Production In Proton Research Articles

D meson production in p+Pb collisions with the analytical transverse momentum distribution from the color dipole models* *Supported by the National Natural Science Foundation of China Joint for Large Scientific Units (U1832120), the Hebei Province Outstanding Youth Fund (A2020210012), the S&T Program of Hebei (Grant No. 236Z4601G), and the Scientific Research Foundation for the Introducing Returned Overseas Chinese Scholars of

D meson production in proton–lead (p+Pb) collisions is globally investigated within the color dipole framework. To simplify the Fourier transform, the analytical transverse momentum distribution functions extracted from different color dipole models are used. With the Glauber–Gribov method, the impact parameter dependence is considered for the nuclear modification of the gluon density. We obtain from comparison with recent experimental data from the LHCb and ALICE Collaborations that the theoretical results from the Kovchegov, Lu and Rezaeian (KLR) model are in good agreement with the experimental data at small P T, and the results from the Golec–Biernat–Wüsthoff (GBW) and Bartels, Golec-Biernat and Kowalski (BGK) model are reasonable at all rapidity bins. Then, the influence of the initial-state energy loss effect on D meson production in p+Pb collisions is analyzed. A clear reduction of the nuclear modification factor is shown at backward rapidity. Finally, the predictive results for D0 and D+ production differential cross section versus rapidity (Y) in p+Pb collisions are given.

Double charmed meson in pp and pA collisions production at the LHC within the dipole approach in momentum representation

A study of double charmed meson production in proton–proton and proton–nucleus collisions at the LHC energies is performed. Based on the color dipole formalism developed in the transverse momentum representation and the double parton scattering mechanism, predictions are made for the transverse momentum differential cross section for different pairs of D-mesons. The theoretical results consider the center-of-mass energy and forward rapidities associated to the measurements by the LHCb Collaboration. The results considering different unintegrated gluon distributions are presented and compared to data and predictions for proton–nucleus collisions are provided.

Direct ρL meson production in proton–proton and proton–antiproton collisions

We have investigated the contribution of the Higher Twist (HT) Feynman diagrams to the large-[Formula: see text] inclusive [Formula: see text] meson production cross-section in proton–proton and proton–antiproton collisions and we discuss the phenomenological consequences of possible HT contributions to cross-sections. To extract HT subprocesses from Leading Twist (LT) background, we use various [Formula: see text] meson distribution amplitudes (DAs). In the numerical calculations, the dependencies of the HT contribution on the transverse momentum and the rapidity are discussed with special emphasis on DAs. Analysis of our results shows that HT contributions decrease more rapidly than LT contributions with increasing [Formula: see text]. The preceding results demonstrate that HT contributions must be considered especially in the region of low [Formula: see text] and the HT contribution to the cross-section depends on the choice of the meson DAs.

Study of K*(892)0 and ϕ (1020) meson production in proton–proton and Pb–Pb collisions at = 2.76 TeV

In this paper, we describe a study of charged particle yield as a function of p T for K *(892)0 and ϕ (1020) mesons in proton–proton (pp) and Pb–Pb collisions at = 2.76 TeV in the central rapidity region of ∣y∣ < 0.5, in a p T range of 0 < p T < 15 GeV c −1 in pp collisions and in a p T range of 0 < p T < 20 GeV c −1 in Pb-Pb collisions. We also investigated a very important ratio, the nuclear modification factor, to study the effects of the medium in the most central region, i.e. 0%–5% centrality. For data simulation, we used the EPOS-LHC and EPOS-1.99 models. To check the validity of these models’ simulations, we compared the data obtained from these Monte Carlo simulation programs with ALICE experimental data for = 2.76 TeV. It was concluded that the models’ predictions for the ϕ-meson in pp and for the most central Pb-Pb collisions disagreed with the ALICE data, and that the difference increased with p T . This may be connected with the essential role of collective parton behaviors which could not have been taken into account by the models. For K *0 mesons, both programs gave almost the same predictions, and with p T in the interval p T > 3 GeV c −1, the predictions were very close to the experimental data. Both models gave higher predictions for the soft p T interval and lower predictions for the hard interactions. The values of the R AA distributions were lower than unity and both models were very close to the ALICE data. It is very interesting that the models were not able to describe the p T distributions, but they gave good predictions for their ratios. This may possibly be due to parton collective behaviors. We observed some additional suppression of K ∗0 at low values of p T with respect to ϕ-mesons, which may be related to the role of the masses of the particles in soft interactions. The rising trend for R AA in the region from p T = 10 GeV c −1 to 20 GeV c −1 observed by the ALICE experiment was absent for the ϕ-mesons.

Meson production in two-photon interaction in pp and pA ultraperipheral collisions at the LHC and FCC

Meson cross-sections are evaluated in two-photon interaction in hadron–hadron ultraperipheral collisions at the CERN Large Hadron Collider (LHC) and Future Circular Collider (FCC). Two models of the equivalent photon flux are employed in the calculations. Cross-sections of meson production in proton–proton and proton-lead ultraperipheral collisions are presented in this paper. These meson cross-sections in two-photon interaction can be applied to predict cross-sections in the experiments at the LHC and FCC.

Measurement of prompt and nonprompt mathrm{J}/{psi } production in mathrm {p}mathrm {p} and mathrm {p}mathrm {Pb} collisions at sqrt{s_{mathrm {NN}}} =5.02,text {TeV}

This paper reports the measurement of mathrm{J}/{psi } meson production in proton–proton (mathrm {p}mathrm {p}) and proton–lead (mathrm {p}mathrm {Pb}) collisions at a center-of-mass energy per nucleon pair of 5.02,text {TeV} by the CMS experiment at the LHC. The data samples used in the analysis correspond to integrated luminosities of 28,text {pb}^{-1} and 35,text {nb}^{-1} for mathrm {p}mathrm {p} and mathrm {p}mathrm {Pb} collisions, respectively. Prompt and nonprompt mathrm{J}/{psi } mesons, the latter produced in the decay of {mathrm {B}} hadrons, are measured in their dimuon decay channels. Differential cross sections are measured in the transverse momentum range of 2<p_{mathrm {T}} <30{,text {GeV}/{c}} , and center-of-mass rapidity ranges of |y_mathrm{{CM}} |<2.4 (mathrm {p}mathrm {p}) and -2.87<y_mathrm{{CM}}<1.93 (mathrm {p}mathrm {Pb}). The nuclear modification factor, R_{mathrm {p}mathrm {Pb}}, is measured as a function of both p_{mathrm {T}} and y_mathrm{{CM}}. Small modifications to the mathrm{J}/{psi } cross sections are observed in mathrm {p}mathrm {Pb} relative to mathrm {p}mathrm {p} collisions. The ratio of mathrm{J}/{psi } production cross sections in mathrm {p}-going and Pb-going directions, R_mathrm{{FB}}, studied as functions of p_{mathrm {T}} and y_mathrm{{CM}}, shows a significant decrease for increasing transverse energy deposited at large pseudorapidities. These results, which cover a wide kinematic range, provide new insight on the role of cold nuclear matter effects on prompt and nonprompt mathrm{J}/{psi } production.

Towards an automated tool to evaluate the impact of the nuclear modification of the gluon density on quarkonium, D and B meson production in proton\u2013nucleus collisions

We propose a simple and model-independent procedure to account for the impact of the nuclear modification of the gluon density as encoded in nuclear collinear PDF sets on two-to-two partonic hard processes in proton–nucleus collisions. This applies to a good approximation to quarkonium, D and B meson production, generically referred to mathcal {H}. Our procedure consists in parametrising the square of the parton scattering amplitude, {mathcal {A}}_{gg rightarrow {mathcal {H}} X} and constraining it from the proton–proton data. Doing so, we have been able to compute the corresponding nuclear modification factors for J/psi , Upsilon and D^0 as a function of y and P_T at sqrt{s_mathrm{NN}}=5 and 8 TeV in the kinematics of the various LHC experiments in a model independent way. It is of course justified since the most important ingredient in such evaluations is the probability of each kinematical configuration. Our computations for D mesons can also be extended to B meson production. To further illustrate the potentiality of the tool, we provide – for the first time – predictions for the nuclear modification factor for eta _c production in pPb collisions at the LHC.

Relativistic corrections to [formula omitted]-pair production in high energy proton–proton collisions

On the basis of perturbative QCD and the relativistic quark model we calculate relativistic corrections to the double ηc meson production in proton–proton interactions at LHC energies. Relativistic terms in the production amplitude connected with the relative motion of heavy quarks and the transformation law of the bound state wave functions to the reference frame of moving charmonia are taken into account. For the gluon and quark propagators entering the amplitude we use a truncated expansion in relative quark momenta up to the second order. Relativistic corrections to the quark bound state wave functions are considered by means of the Breit-like potential. It turns out that the examined effects decrease total non-relativistic cross section more than two times and on 20 percents in the rapidity region of LHCb detector.

Analysis Method of ϕ-meson Production in Proton–Proton Collisions in the NA61/SHINE Experiment at the CERN SPS

Analysis Method of <span class="cmmi-10">ϕ</span>-meson Production in Proton–Proton Collisions in the NA61/SHINE Experiment at the CERN SPS

Neutral pion and η meson production in proton–proton collisions at [formula omitted] and [formula omitted

The first measurements of the invariant differential cross sections of inclusive π0 and η meson production at mid-rapidity in proton–proton collisions at s=0.9 TeV and s=7 TeV are reported. The π0 measurement covers the ranges 0.4<pT<7 GeV/c and 0.3<pT<25 GeV/c for these two energies, respectively. The production of η mesons was measured at s=7 TeV in the range 0.4<pT<15 GeV/c. Next-to-Leading Order perturbative QCD calculations, which are consistent with the π0 spectrum at s=0.9 TeV, overestimate those of π0 and η mesons at s=7 TeV, but agree with the measured η/π0 ratio at s=7 TeV.

THE MESON PRODUCTION IN PROTON–PROTON COLLISIONS IN NEXT-TO-LEADING ORDER AND INFRARED RENORMALONS

In this paper, we investigate the next-to-leading order contribution of the higher-twist Feynman diagrams to the large-pT inclusive pion production cross-section in proton–proton collisions and present the general formulae for the higher-twist differential cross-sections in the case of the running coupling and frozen coupling approaches. We compared the resummed next-to-leading order higher-twist cross-sections with the ones obtained in the framework of the frozen coupling approach and leading-twist cross-section. The structure of infrared renormalon singularities of the higher-twist subprocess cross-section and its resummed expression (the Borel sum) are found. It is shown that the resummed result depends on the choice of the meson wave functions used in the calculations. We discuss the phenomenological consequences of possible higher-twist contributions to the meson production in proton–proton collisions in next-to-leading order at RHIC.

Elastic double diffractive production of axial-vector [formula omitted] mesons and the Landau–Yang theorem

We discuss exclusive elastic double diffractive axial-vector χc(1+) meson production in proton–antiproton collisions at the Tevatron. The amplitude for the process is derived within the kt-factorization approach with unintegrated gluon distribution functions (UGDFs). We show that the famous Landau–Yang theorem is not applicable in the case of off-shell gluons. Differential cross sections for different UGDFs are calculated. We compare exclusive production of χc(1+) and χc(0+). The contribution of χc(1+) to the J/Ψ+γ channel is smaller than that of the χc(0+) decay, but not negligible and can be measured. The numerical value of the ratio of the both contributions is much less dependent on the UGDFs modeling than the cross sections themselves.

Near-threshold ϕ meson production in proton–nucleus reactions and ϕ width in finite nuclei

In the framework of the nuclear spectral function approach for incoherent primary proton–nucleon and secondary pion–nucleon production processes, we study the inclusive ϕ meson production in the interaction of 2.83 GeV protons with nuclei. In particular, the A and momentum dependences of the absolute and relative ϕ meson yields are investigated within the different scenarios for its in-medium width. Our model calculations take into account the acceptance window of the ANKE facility used in a recent experiment performed at COSY. They show that the pion–nucleon production channel contributes distinctly to the ‘low-momentum’ ϕ creation in heavy nuclei in the chosen kinematics and, hence, has to be taken into consideration on close examination of the dependences of the phi meson yields on the target mass number with the aim to get information on its width in the medium. They also demonstrate that both the A-dependence of the relative ϕ meson production cross section and momentum dependence of the absolute ϕ meson yield at incident energy of interest are appreciably sensitive to the phi in-medium width, which means that these observables can be useful to help determine the above width from the direct comparison of the results of our calculations with the future data from the respective ANKE-at-COSY experiment.

Analyzing power [formula omitted] for ω meson production in proton–proton collisions

We report on a determination of the analyzing power Ay in the p→p→ppω reaction studied with the TOF spectrometer located at the COSY-accelerator (Forschungszentrum Jülich, Germany). This spectrometer is very well suited for polarization measurements due to its rotational symmetry and full coverage of the azimuthal angle. For a beam momentum of p=3065 MeV/c corresponding to an excess energy of ϵ=129 MeVAy is found to be compatible with zero.

SIGMA MESON PRODUCTION IN HEAVY ION COLLISIONS AT INTERMEDIATE ENERGIES

The production of the sigma (σ) meson is investigated in the quantum molecular dynamics model for the p+A reactions with the nuclei A being 12 C , 40 Ca and 208 Pb at the incident proton energies Ep = 1.50 GeV . The simulation results indicates a distinctive A dependence of the sigma production, that is, the increase of A is followed by an increase of the production cross-sections. The σ meson production in proton induced reactions is strongly medium-dependent, and the produced σ mesons decaying in a denser medium experience a stronger mass shift towards lower masses. This mass shift is an experimentally accessible observable in the final state pion pairs which did not suffer reabsorption by the surrounding nucleons. It is pointed out that the ratio of the simulation results of measurable σ mesons (in the form of two pions) cross-sections as a function of the sigma invariant-mass from various reactions opens the possibility to address experimentally the mass shift of the σ in a dense nuclear environment.

K*0 and φ meson production in proton–nucleus interactions at $\sqrt{s}=41.6\text{GeV}$

The inclusive production cross sections of the strange vector mesons K*0, K*0bar, and phi have been measured in interactions of 920 GeV protons with C, Ti, and W targets with the HERA-B detector at the HERA storage ring. Differential cross sections as a function of rapidity and transverse momentum have been measured in the central rapidity region and for transverse momenta up to pT=3.5 GeV/c. The atomic number dependence is parametrised as sigma(pA) = sigma(pN)*A**alpha, where sigma(pN) is the proton-nucleon cross section. Within the phase space accessible, alpha(K*0) = 0.86+/-0.03, alpha(K*0bar) = 0.87+/-0.03, and alpha(phi) = 0.96+/-0.02. The total proton-nucleon cross sections, determined by extrapolating the differential measurements to full phase space, are sigma(pN->K*0) = 5.06+/-0.54 mb, sigma(pN->K*0bar) = 4.02+/-0.45 mb, and sigma(pN->phi) = 1.17+/-0.11 mb. The Cronin effect is observed for the first time for vector mesons containing strange quarks; compared to the measurements of Cronin et al. for K+- mesons, the measured values of alpha for phi mesons coincide with those of K- mesons for all transverse momenta, while the enhancement for K*0 / K*0bar mesons is smaller.

A precision determination of the mass of the η meson

Several processes of meson production in proton–deuteron collisions have been measured simultaneously using a calibrated magnetic spectrograph. Among these processes, the η meson is seen clearly as a sharp missing-mass peak on a slowly varying background in the p+d→He3+X reaction. Knowing the kinematics of the other reactions with well determined masses, it is possible to deduce a precise mass for the η meson. The final result, m(η)=547.311±0.028(stat)±0.032(syst)MeV/c2, is significantly lower than that found by the recent NA48 measurement, though it is consistent with values obtained in earlier counter experiments.

Near-threshold η meson production in proton–proton collisions

The production of η mesons has been measured in the proton-proton interaction close to the reaction threshold using the COSY-11 internal facility at the cooler synchrotron COSY. Total cross sections were determined for eight different excess energies ( ϵ) in the range from ϵ=0.5 MeV to ϵ=5.4 MeV. The energy dependence of the total cross section is well described by the available phase–space volume weighted by FSI factors for the proton–proton and proton– η pairs.

Subthreshold K + meson production in proton–nucleus reactions and nucleon spectral function

The inclusive K+ mesons production in proton-nucleus collisions in the near threshold and subthreshold energy regimes is analyzed with respect to the one-step (pN->K+YN, Y=Lambda,Sigma) and the two-step (pN->NNpi, NN2pi; piN->K+Y) incoherent production processes on the basis of an appropriate new folding model, which takes properly into account the struck target nucleon removal energy and momentum distribution (nucleon spectral function), extracted from recent quasielastic electron scattering experiments and from many-body calculations with realistic models of the NN interaction. Comparison of the model calculations of the K+ double differential cross sections for the reaction p+C at 1.2, 1.5 and 2.5 GeV beam energies with the existing experimental data from the SATURNE experiment is given, illustrating both the relative role of the primary and secondary production channels at considered incident energies and those features of the cross sections which are sensitive to the high momentum and high removal energy part of the nucleon spectral function that is governed by nucleon-nucleon short-range and tensor correlations. In--medium modifications of the available for pion and hyperon production invariant energies squared due to the respective optical potentials are needed to account for the experimental data on K+ production in the energy region under consideration.

Meson production inp+U, O+U and S+U interactions at 200 GeV/nucleon

Meson production in proton, oxygen and sulphur interactions with uranium targets at 200 GeV/nucleon is studied. We measure the inclusive meson cross-section d σ/dPT2 and its evolution fromp+U to S+U. The cross-section fitted with an exponential gives an inverse slopePT0 of the order of 210 MeV/c. As a function of the neutral transverse energy,PT0 values show a slight rise followed by a plateau. The normalized difference (σ+−σ−)/σ− between positive and negative meson cross-sections is found to increase withET.