The production of K+K- pairs in proton-proton collisions at 2.83 GeV
Q. J. Ye, M. Hartmann, Y. Maeda, S. Barsov, M. Buescher, D. Chiladze, S. Dymov, A. Dzyuba, H. Gao, R. Gebel, V. Hejny, A. Kacharava, I. Keshelashvili, Yu. T. Ki… 展开作者
Q. J. Ye, M. Hartmann, Y. Maeda, S. Barsov, M. Buescher, D. Chiladze, S. Dymov, A. Dzyuba, H. Gao, R. Gebel, V. Hejny, A. Kacharava, I. Keshelashvili, Yu. T. Kiselev, A. Khoukaz, V. P. Koptev, P. Kulessa, A. Kulikov, B. Lorentz, T. Mersmann, S. Merzliakov, S. Mikirtytchiants, M. Nekipelov, H. Ohm, E. Ya. Paryev, A. Polyanskiy, V. Serdyuk, H. J. Stein, H. Stroeher, S. Trusov, Yu. Valdau, C. Wilkin, P. Wuestner
Differential and total cross sections for the pp -> ppK+K- reaction have been measured at a proton beam energy of 2.83 GeV using the COSY-ANKE magnetic spectrometer. Detailed model descriptions fitted to a variety of one-dimensional distributions permit the separation of the pp -> pp phi cross section from that of non-phi production. The differential spectra show that higher partial waves represent the majority of the pp -> pp phi total cross section at an excess energy of 76 MeV, whose energy dependence would then seem to require some s-wave phi-p enhancement near threshold. The non-phi data can be described in terms of the combined effects of two-body final state interactions using the same effective scattering parameters determined from lower energy data.
We comment on the statement by Kuznetsov et al. that the structure around W=1.72 GeV seen in the beam asymmetry in Compton scattering off the proton is not observed in the total cross section of $η$ photoproduction on the neutron.
Energy and centrality dependence of antiproton and proton production and the antilambda to antiproton ratio in Pb+Pb collisions between 20A GeV and 158A GeV
Initial state geometry and the role of hydrodynamics in proton-proton, proton-nucleus and deuteron-nucleus collisions
我们将成功的重离子碰撞的Monte Carlo Glauber和IP-Mehma初态模型应用于质子-质子、质子-核和氘-核碰撞中产生的小得多的系统。我们观察到一个显着更大的灵敏度的初始状态的几何形状，在这些模型中的多粒子生产的细节相比，核-核碰撞。特别是，我们发现，在p+A碰撞中产生的系统的大小是非常相似的p+p碰撞中产生的，并预测可比的Hanbury-Brown-Twiss半径在两个系统中没有流动。模型中计算的偏心率差异较大，而生成的流量系数v_2和v_3之间的差异较小。对于大量的质子-铅碰撞的参与者，在IP-Plumma模型中产生的v_2值与质子-质子碰撞中获得的值相当。在较小尺寸的系统中，对流动的粘性修正在特征寿命上是大的。相反，粘性的贡献显着减少了较长的时空演化的重离子碰撞。
The study of multiparticle correlations and collectivity in the hot and dense matter created in collisions of heavy-ions as well as those of smaller systems such as proton--heavy-ion collisions has progressed to the point where detailed knowledge of the three-dimensional structure of the proton is needed to confront experimental data. We discuss results from a simple proof-of-principle initial state parton model which reproduces many features of the data on proton--heavy-ion collisions that are often ascribed to hydrodynamic flow. We outline how this model can be further improved with particul…
It is argued that the multiplicity distribution in proton-proton ($pp$) collisions, which is often parameterized by the negative binomial distribution, may result from the multiplicity distribution measured in electron-positron ($e^{+}e^{-}$) collisions, once the fluctuating energy carried by two leading protons in $pp$ is taken into account.
The proton--proton elastic differential cross section at very small four momentum transfer squared has been measured at three different incident proton momenta in the range of 2.5 to 3.2 GeV/c by detecting the recoil proton at polar angles close to $90^\circ$. The measurement was performed at COSY with the KOALA detector covering the Coulomb-nuclear interference region. The total cross section $σ_\text{tot}$, which has been determined precisely, is consistent with previous measurements. The values of the slope parameter $B$ and the relative real amplitude ratio $ρ$ determined in this experimen…
The inclusive charged particle transverse momentum distribution is measured in proton-proton collisions at $\sqrt{s} = 900$ GeV at the LHC using the ALICE detector. The measurement is performed in the central pseudorapidity region $(|η|<0.8)$ over the transverse momentum range $0.15<p_{\rm T}<10$ GeV/$c$. The correlation between transverse momentum and particle multiplicity is also studied. Results are presented for inelastic (INEL) and non-single-diffractive (NSD) events. The average transverse momentum for $|η|<0.8$ is $\left<p_{\rm T}\right>_{\rm INEL}=0.483\pm0.001$ (stat.) $\pm0.007$ (sys…
In this contribution we report $e^{+}e^{-}$ spectra with various invariant mass and p$_{T}$ differentials in Au$+$Au collisions at $\sqrt{s_{NN}}$=200 GeV and U$+$U collisions at $\sqrt{s_{NN}}$=193 GeV. The structure of the t ($t\approx p^2_{\mathrm{T}}$) distributions of these mass regions will be shown and compared with the same distributions in ultra-peripheral collisions. Additionally, this contribution discusses first measurements of $μ^{+}μ^{-}$ invariant mass spectra from STAR's recently installed Muon Telescope Detector (MTD) in p$+$p and Au$+$Au collisions at $\sqrt{s_{NN}}$ = 200 Ge…
The proton-proton ($pp$) collisions at the Large Hadron Collider (LHC), CERN, Switzerland has brought up new challenges and opportunities in understanding the experimental findings in contrast to the conventional lower energy $pp$ collisions. Usually $pp$ collisions are used as the baseline measurement at the GeV and TeV energies in order to understand a possible high density QCD medium formation in heavy-ion collisions. However, the TeV $pp$ collisions have created a new domain of research, where scientists have started observing heavy-ion-like features (signatures) in high-multiplicity $pp$ …
Proton-proton ($pp$) collision has been considered as a baseline to study the system produced in relativistic heavy-ion (AA) collisions with the basic assumption that no thermal medium is formed in $pp$ collisions. This warrants a cautious analysis of the system produced in $pp$ collisions at relativistic energies.In this work we investigate the charmonium suppression in $pp$ collisions at $\sqrt{s} = 5.02, 7$ and $13$ TeV energies. Further, charmonium suppression has been studied for various event multiplicities and transverse momenta by including the mechanisms of color screening, gluonic di…
Particle production mechanisms in proton+proton and heavy-ion collisions at the LHC energies are discussed. An attempt is made to connect p+p to heavy-ion collisions in understanding the final state observables. New emerging phenomena like Multipartonic Interactions (MPI) and Color Reconnection (CR) mechanism are important in understanding heavy-ion like behaviors in high-multiplicity p+p events. Particle spectra, Multipartonic Interactions, Strangeness enhancement, Nuclear modification factor etc. are few of the aspects, which are discussed in this presentation.
In these proceedings, we present the higher-order cumulants of proton multiplicity distributions of the fixed-target (FXT) run in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 3.0 GeV. The cumulant ratios are presented as a function of centrality and collision energy. The proton cumulant ratio C4/C2 is consistent with fluctuations driven by baryon number conservation and indicates an energy regime dominated by hadronic interactions. These data imply that the QCD critical point could exist at energies higher than 3 GeV if created in heavy-ion collisions.
The first result of the pp2pp experiment at RHIC on elastic scattering of polarized protons at sqrt{s} = 200 GeV is reported here. The exponential slope parameter b of the diffractive peak of the elastic cross section in the t range 0.010 <= |t| <= 0.019 (GeV/c)^2 was measured to be b = 16.3 +- 1.6 (stat.) +- 0.9 (syst.) (GeV/c)^{-2} .
We report the first results on differential, total and elastic cross sections in proton-proton collisions at the Relativistic Heavy Ion Collider (RHIC) at $\sqrt{s}=200$ GeV. The data lwere obtained with the Roman Pot Detector subsystem of the STAR experiment. The data used for this analysis cover the four-momentum transfer squared ~($t$) range $ 0.045 \le |t| \le 0.135$ (GeV/c)$^2$. The Roman Pot system was placed downstream of the STAR detector. During the data taking the Roman Pots were moved to ~8$σ_{y}$, the vertical distance of from the beam center. They were operated during standard dat…
Although transverse-mass scaling of femtoscopic radii is found to hold to a good approximation in heavy-ion collision experiments, it is seen to fail for high-energy proton-proton collisions. It is shown that if invariant radius parameters are plotted versus the transverse velocity instead, scaling with the transverse velocity is seen in $\sqrt{s}=7$ TeV proton-proton experiments. A simple semi-classical model is shown to qualitatively reproduce this transverse velocity scaling.
The production of jets in polarized proton collisions at STAR is dominated by quark-gluon and gluon-gluon scattering processes. The dijet longitudinal double-spin asymmetry $(A_{LL})$ is sensitive to the helicity distributions and may be used to extract information about the gluon helicity contribution $Δ{g(x,Q^2)}$ to the spin of the proton. Previous STAR jet measurements at $\sqrt s$ = 200 GeV show evidence of polarized gluons for gluon momentum fractions above 0.05. The measurement of dijet $A_{LL}$ at $\sqrt s$ = 510 GeV will extend the current constraints on $Δ{g(x,Q^2)}$ to lower gluon m…
