In asymmetric heavy ion collisions like dA or pA, particle production yields are different in the forward (d- or p-side) and backward (A-side) rapidity directions. The rapidity distribution reflects the geometry and phase-space distribution of nuclear matter. These properties may depend on the time evolution of the collision. Due to the smallness of the backward-forward differences, the rapidity asymmetry factor can be useful to quantify nuclear modification effects, like e.g. shadowing and the EMC effect. Our work is a survey of the nuclear modification factor and the rapidity asymmetries at RHIC energies. We analyze the rapidity dependence and the strength of the nuclear effects. We focus on the high transverse momentum region, and make predictions for the role of nuclear modifications and rapidity asymmetries for future experimental measurements at increasing absolute values of rapidity.
We investigate the scaling properties in inclusive hadron production and the associated single transverse spin asymmetry in the forward rapidity region at RHIC. We find that the spin-averaged experimental data in both $pp$ and $dAu$ collisions demonstrates a transverse-momentum-dependent geometric scaling. We introduce the transverse momentum dependent Collins fragmentation function to study the scaling of the single transverse spin asymmetries. The general feature of the scaling analysis is consistent with the experimental observations, in particular, for the transverse momentum dependence of…
We calculate pseudorapidity ($η$) asymmetry in $pA$ and $dA$ collisions in a pQCD-improved parton model. With the calculations tuned to describe existing spectra from $pp$ collisions and asymmetric systems at midrapidity and large rapidities at FNAL and RHIC energies, we investigate the roles of nuclear shadowing and multiple scattering on the observed asymmetry. Using this framework, we make predictions for pseudorapidity asymmetries at high $p_T$ and large $η$ in a wide range of energies up to LHC.
I present results for the top quark rapidity distribution at LHC and Tevatron energies, including higher-order corrections from threshold resummation. The next-to-next-to-leading-order (NNLO) soft-gluon corrections at next-to-next-to-leading-logarithm (NNLL) level are added to the NLO result. Theoretical predictions are shown for the rapidity distribution, including the scale dependence of the distributions. The forward-backward asymmetry at the Tevatron is also calculated.
Interpretation of long-range rapidity correlations in terms of the fluctuating rapidity density distribution of the system created in high-energy collisions is proposed. When applied to recent data of the STAR coll., it shows a substantial asymmetric component in the shape of this system in central Au-Au collisions, implying that boost invariance is violated on the event-by-event basis even at central rapidity. This effect may seriously influence the hydrodynamic expansion of the system.
In contrast to the recent prediction of high $p_T$ hadron suppression within the parton saturation model, it is shown that multiple parton scattering suffered by the projectile will enhance high $p_T$ hadron spectra in $d+A$ collisions relative to a superposition of binary $p+p$ collisions at RHIC. A stronger enhancement in the forward rapidity region of the projectile is also predicted, resulting in a unique rapidity asymmetry of the hadron spectra at high $p_T$. The shape of the rapidity asymmetry should be reversed for low $p_T$ hadrons that are dominated by soft and coherent interactions w…
We study the invariant mass and rapidity dependent top quark forward-backward asymmetry from the effective Lagrangian viewpoint. The Wilson coefficients are constrained by the experimental observations and the concrete models that reproduce the low energy effective Lagaragians are considered. Some of them are disfavored and others relatively favored. For each cases, we estimate the appropriacy of the effective Lagrangian approach.
We make use of recent results in effective theory and higher-order perturbative calculations to improve the theoretical predictions of the QCD contribution to the top-quark pair production forward-backward asymmetry at the Tevatron. In particular, we supplement the fixed-order NLO calculation with higher-order corrections from soft gluon resummation at NNLL accuracy performed in two different kinematic schemes, which allows us to make improved predictions for the asymmetry in the $p\bar p$ and $t\bar t$ rest frames as a function of the rapidity and invariant mass of the $t\bar t$ pair. Further…
Most signatures of new physics have been studied on the transverse plane with respect to the beam direction at the LHC where background is much reduced. In this paper we propose the analysis of inclusive longitudinal (pseudo)rapidity correlations among final-state (charged) particles in order to search for (un)particles belonging to a Hidden Sector beyond the Standard Model, using a selected sample of p-p minimum bias events (applying appropriate off-line cuts on events based on, e.g., minijets, high-multiplicity, event shape variables, high-pT leptons and photons, etc) collected at the early …
We investigate the production of the weak bosons $W^+$, $W^-$ and $Z$ at the LHC as a function of their rapidity, reconstructed {\it experimentally} from their leptonic decay. We show that the measurements provide a powerful tool for constraining the parton distribution functions, as was already the case for the lower energy $p\bar{p}$ collider data. We study the charge asymmetry determining the $u$ and $d$ distribution functions using the reconstructed $W^+$, $W^-$ rapidities. We also show how the ratio of the $W$ and $Z$ boson rapidity distributions directly probes the charm quark distributi…
Using the latest quark Sivers functions extracted from the global analysis of available data on single transverse spin asymmetry (SSA), we calculate the SSA of Drell-Yan inclusive production of lepton pairs of invariant mass $Q$ at both $4<Q<9$ GeV and $Q\sim M_Z$ in $p^\uparrow p$ collisions at RHIC energies. We find that the features of the asymmetry $A_N$ for $Q\sim M_Z$ are significantly different from that when $4<Q<9$ GeV. The $A_N$ near $Z^0$ pole is positive and sizable in the central rapidity region while the $A_N$ at low $Q$ is negative and only sizable in the forward rapidity region…
The nuclear modification factor $R_{AA}$ for $π_0$ production in Au+Au collisions at $\sqrt{s}=200$ AGeV is calculated, and studied at high transverse momenta $p_T$. The soft thermalized nuclear medium is described within the framework of relativistic ideal three-dimensional hydrodynamics. The energy loss of partonic jets is evaluated in the context of gluon bremsstrahlung in the thermalized partonic matter. We provide a systematic analysis of the azimuthal asymmetry of $π_0$ suppression at high $p_T$ in central and non-central collisions, at mid and forward rapidity. The determination of $R_{…
At the LHC, top quark pairs are dominantly produced from gluons, making it difficult to measure the top quark forward-backward asymmetry. To improve the asymmetry measurement, we study variables that can distinguish between top quarks produced from quarks and those from gluons: the invariant mass of the top pair, the rapidity of the top-antitop system in the lab frame, the rapidity of the top quark in the top-antitop rest frame, the top quark polarization and the top-antitop spin correlation. We combine all the variables in a likelihood discriminant method to separate quark-initiated events fr…
The recent experimental results on CP violation related to the angles of the Cabibbo-Kobayashi-Maskawa (CKM) unitarity triangle 2beta+gamma are summarized in these proceedings. These results are obtained with approximately 232 million Y4S->BBbar events collected with the BABAR detector at the PEP-II asymmetric-energy B-factory at SLAC. Using the measurements on time-dependent CP asymmetries in B0->D(*)-+pi+- and B0->D-+rho+- decays and theoretical assumptions, one finds |sin(2beta+gamma)|>0.64 (0.40) at 68% (90%) confidence level. The perspectives of sin(2beta+gamma) measurement with B0bar-> D…
A significant asymmetry in baryon/antibaryon yields in the central region of high energy collisions is observed when the initial state has non-zero baryon charge. This asymmetry is connected with the possibility of a baryon charge diffusion in rapidity space. Evidently, such a diffusion should decrease the baryon charge in the fragmentation region leading to the corresponding decrease of the multiplicity of leading baryons. As a result, a new mechanism for Feynman scaling violation in the fragmentation region is obtained. We present the quantitative predictions for the Feynman scaling violatio…
School of Physics and Astronomy, China West Normal Universty（西华师范大学物理与天文学院）；School of Physics and Electronic Engineering, Sichuan University of Science and Engineering（四川理工学院物理与电子工程学院）；Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University（华中师范大学夸克与轻子物理教育部重点实验室及粒子物理研究所）
A comparative study of amplitude zeros in $Wγ$ and $WZ$ production in hadronic collisions is presented. The Standard Model amplitude for $q_1 \bar q_2 \rightarrow W^\pm Z $ at the Born-level is shown to exhibit an approximate zero located at $\cosθ= (g^{q_1}_{-} + g^{q_2}_{-}) / (g^{q_1}_{-} - g^{q_2}_{-})$ at high energies, where the $g^{q_i}_{-}$ ($i=1,2$) are the left-handed couplings of the $Z$-boson to quarks and $θ$ is the center of mass scattering angle of the $W$-boson. This approximate zero is similar to the well-known radiation zero in $Wγ$ production. Prospects to observe the amplit…
We discuss production of neutral $D$ mesons in proton-proton collisions at the LHC (fixed target mode) in the framework of the BJM recombination model. We present rapidity and transverse momentum distributions of $D$ mesons and compare the recombination contribution to the dominant gluon-gluon fusion mechanism. Both the direct production, as dictated by the matrix element, and fragmentation of the associated $c$ or $\bar c$ are included. The latter mechanism generates $D$ mesons with smaller rapidities than those produced directly. We calculate the $D^0 + {\bar D^{0}}$ meson distributions rele…
The measurement of the polarized gluon distribution function Delta G(x) from photon-gluon fusion processes in electron-proton deep inelastic scattering producing two jets has been investigated. The study is based on the MEPJET and PEPSI simulation programs. The size of the expected spin asymmetry and corresponding statistical uncertainties for a possible measurement with polarized beams of electrons and protons at HERA have been estimated. The results show that the asymmetry can reach a few percent, and is not washed out by hadronization and higher order processes.
We show that the double diffractive electroweak vector boson production in the $pp$ collisions at the LHC is an ideal probe of QCD based mechanisms of diffraction. Assuming the resolved Pomeron model with flavor symmetric parton distributions, the $W$ production asymmetry in rapidity equals exactly zero. In other approaches, like the soft color interaction model, in which soft gluon exchanges are responsible for diffraction, the asymmetry is non-zero and equal to that in the inclusive $W$ production. In the same way, the ratio of the $W$ to $Z$ boson production is independent of rapidity in th…
The charge asymmetry in hadronic top-antitop-quark production is a powerful test observable of perturbative quantum chromodynamics. Since its origin in terms of Feynman diagrams is distinct from charge-symmetric top-antitop production, probing the charge asymmetry provides complementary information to cross section measurements. Furthermore, asymmetric observables offer new ways to distinguish new physics beyond the standard model. This article summarizes prospects to investigate the top-quark charge asymmetry at the LHC in and beyond the standard model. Particular attention is given to observ…
The measurement of the polarized gluon distribution function $Δg(x)$ from photon gluon fusion processes in electron proton deep inelastic scattering producing two jets has been investigated. The study is based on the MEPJET simulation program. The size of the expected spin asymmetry and corresponding statistical uncertainties for a possible measurement with polarized beams of electrons and protons at HERA have been estimated. The results show that the asymmetry can reach a few percents.
This study focuses on hard diffractive events produced in proton-proton collision at LHC exhibiting one intact proton in the final state which can be tagged by forward detectors. We report prospective results on the W boson charge asymmetry measured for such events, which allow to constrain the quark diffractive density functions in the Pomeron.
The spin structure of the proton has revealed itself to be extremely complex and is an area of ongoing research. The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) inaugurated its operation as the first polarized-proton collider during the 2001-2002 run, marking the beginning of a new era in the study of proton spin structure. From the data collected in this run, the PHENIX experiment measured the transverse single-spin asymmetry (A_N) for neutral pion production at x_F~0.0 over a transverse momentum range of 1 to 5 GeV/c from polarized proton-proton interaction…
I present a calculation of approximate N$^3$LO corrections from NNLL soft-gluon resummation for differential distributions in top-antitop pair production in hadronic collisions. Soft-gluon corrections are the dominant contribution to top-quark production and closely approximate exact results through NNLO. I show aN$^3$LO results for the total $t{\bar t}$ cross section, the top-quark $p_T$ and rapidity distributions, and the top-quark forward-backward asymmetry. The higher-order corrections are significant and they reduce theoretical uncertainties.
The forward-backward asymmetry in top pair production at Tevatron has been reconfirmed by the CDF collaboration with 5.3 fb^{-1} of accumulated data. These measurements also report that the asymmetry is the largest in regions of high invariant mass M_{t\bar{t}} and rapidity difference |ΔY|. We consider light colored sextet scalars appearing in a particular non-supersymmetric \10 grand unification model within the \bar{126} scalar representation. These scalar states have masses in the range of 300 \text{GeV}-2 \text{TeV} consistent with the requirements of gauge coupling unification and bounds …
After the observation of non-zero $θ_{13}$ the goal has shifted to observe $CP$ violation in the leptonic sector. Neutrino oscillation experiments can, directly, probe the Dirac $CP$ phases. Alternatively, one can measure $CP$ violation in the leptonic sector using Leptonic Unitarity Quadrangle(LUQ). The existence of Standard Model (SM) gauge singlets - sterile neutrinos - will provide additional sources of $CP$ violation. We investigate the connection between neutrino survival probability and rephasing invariants of the $4\times4$ neutrino mixing matrix. In general, LUQ contain eight geometri…
An influence of the anomalous Wtb coupling on forward-backward asymmetry of top quark pair production at the Tevatron is investigated taking into account decays of the top quarks to 6 fermion final states containing one charged lepton. To this end the most general effective Lagrangian of the Wtb interaction containing terms of dimension up to five is implemented into 'carlomat', a general purpose Monte Carlo program, which allows to compute automatically all necessary cross sections in the presence of anomalous vector and tensor form factors. A sample of results which illustrate little effect …
The neutrino oscillation probabilities in vacuum and matter are discussed, considering the framework of three active and one light sterile neutrinos. We study in detail the rephasing invariants and CP asymmetry observables, and investigate the four-neutrino oscillations in long-baseline neutrino experiments, such as DUNE, NO$ν$A and T2HK. Our results show that the matter effect enhances quite a significantly the oscillation probabilities of electron neutrino and electron antineutrino appearance channels within a certain energy range, while no considerable change arises in the CP asymmetry anal…
Using the CGC formalism, we calculate the two-gluon rapidity correlations of strong colour fields in $pp$, $pA$ and $AA$ collisions, respectively. If one trigger gluon is fixed at central rapidity, a ridge-like correlation pattern is obtained in symmetry $pp$ and $AA$ collisions, and a huge bump-like correlation pattern is presented in asymmetry $pA$ collisions. It is demonstrated that the ridge-like correlation patterns are caused by the stronger correlation with the gluon of colour source. The transverse momentum and incident energy dependence of the ridge-like correlation pattern is also sy…
We describe a comprehensive survey of two-particle correlations from p-p collisions at $\sqrt{s} = 200$ GeV. Correlations on transverse rapidity $y_t$ are separated into a soft component (string fragments) and a hard component (parton fragments). Fragment correlations on transverse rapidity $y_t$ are compared to fragmentation functions on logarithmic momentum variable $ξ$. Cuts on transverse rapidity isolate angular correlations on $(η,ϕ)$ for the two components. Hard-component angular correlations are compared to results from conventional leading-particle jet analysis. Angular correlations fo…
We propose the boost asymmetry of the diboson productions in pp collisions as a new experimental observable, which can provide unique information on the proton structure. The boost asymmetry rises as the difference in the kinematics of the two bosons, that are coupled to the two different quark and antiquark initial states, respectively, and thus reflects different features of the quark and antiquark parton densities. By comparing the kinematics of the two bosons, such as the boson energy or rapidity, the diboson events with antiquark having higher energy than quark can be distinguished from t…
We study the rapidity dependence of the cross section on the rapidity of the central exclusive production cross sections of C-even mesons in $pA$ and $AA$ collisions, where $A$ is a heavy ion. We observe qualitatively different behaviour of the contributions arising from $γ$-Odderon and Pomeron-Pomeron fusion mechanisms. This can be used to extract the Odderon signal from the events of $f_2$ mesons exclusively produced in the forward region. Estimates, obtained using expected values of the Odderon cross section, indicate that the $γ$-Odderon contribution may exceed by a few times the Pomeron-i…
The search for a possible critical point in the QCD phase diagram is ongoing in heavy ion collision experiments at RHIC which scan the phase diagram by scanning the beam energy; a coming upgrade will increase the luminosity and extend the rapidity acceptance of the STAR detector. In fireballs produced in RHIC collisions, the baryon density depends on rapidity. By employing Ising universality together with a phenomenologically motivated freezeout prescription, we show that the resulting rapidity dependence of cumulant observables sensitive to critical fluctuations is distinctive. The dependence…
The measured forward-backward asymmetry in top pair events at the Fermilab Tevatron collider deviates significantly from the standard model expectation. Several models have been proposed to describe the observed asymmetry which grows with the rapidity difference of the top pairs and also with the $t\bar{t}$ invariant mass. The presence of a heavy charged gauge boson $W'$ with the coupling $W'-t-d$ (left-handed, right-handed, and a mixture of left and right-handed couplings) could generate the desired top forward-backward asymmetry keeping the top pair cross section consistent with the standard…
We use the string melting version of a multi-phase transport (AMPT) model to study Cu+Au collisions at $\sqrt{s_{NN}}=200$ GeV. The rapidity distributions of identified hadrons show asymmetric dependences on rapidity. In addition, elliptic and triangular flows at mid-rapidity from the AMPT model for pions, kaons, and protons agree reasonably with the experimental data up to $p_{T}\sim1$ GeV$/c$. We then investigate the forward/backward asymmetry of $v_2$ and $v_3$. We find that these anisotropic flows are larger on the Au-going side than the Cu-going side, while the asymmetry tends to go away …
Measurements of the forward-backward asymmetry in neutral-current Drell-Yan di-lepton production have primarily been used for determinations of the weak mixing angle $θ_W$. We observe that, unlike the case of Run-I of the Large Hadron Collider (LHC Run-I), for the first time at the LHC Run-II the reconstructed forward-backward asymmetry has the capability of placing useful constraints on the determination of the parton distribution functions (PDFs). By examining the statistical and the PDF uncertainties on the reconstructed forward-backward asymmetry, we investigate its potential for disentang…
There is a well-established relation between the spatial asymmetry in the initial stage of a heavy-ion collision and the final momentum anisotropy, which allows for a separation of effects from initial conditions vs. later evolution and has proved exceptionally powerful. However, until recently it has only been studied in two dimensions -- either through boost-invariant simulations or studying only quantities at mid-rapidity. We explore an extension to 3 dimensions, in order to determine whether a similar understanding can be obtained for the rapidity dependence of the collision system. In par…
The Tevatron has measured a discrepancy relative to the Standard Model prediction in the forward-backward asymmetry in top quark pair production. This asymmetry grows with the rapidity difference of the two top quarks. It also increases with the invariant mass of the tt pair, reaching, for high invariant masses, 3.4 standard deviations above the Next to Leading Order prediction for the charge asymmetry of QCD. However, perfect agreement between experiment and the Standard Model was found in both total and differential cross section of top quark pair production. As this result could be a sign o…
We use techniques from soft-collinear effective theory (SCET) to derive renormalization-group improved predictions for single-particle inclusive (1PI) observables in top-quark pair production at hadron colliders. In particular, we study the top-quark transverse-momentum and rapidity distributions, the forward-backward asymmetry at the Tevatron, and the total cross section at NLO+NNLL order in resummed perturbation theory and at approximate NNLO in fixed order. We also perform a detailed analysis of power corrections to the leading terms in the threshold expansion of the partonic hard-scatterin…
To extract information about polarized gluons in the proton, production of charmed hadrons, in particular, Λ_c^+ baryon in pp collisions was studied. We calculated the transverse momentum distribution and the pseudo-rapidity distribution of the spin correlation asymmetry A_{LL} between the initial proton and the produced Λ_c^+. Those statistical sensitivities were also calculated under the condition of RHIC experiment. We found that the pseudo-rapidity distribution of A_{LL} is promising for testing the model of polarized gluons in the proton and also the spin-dependent fragmentation model of …
We calculate the rapidity dependence of the transverse double-spin asymmetry for the Drell-Yan process to next-to-leading order in the strong coupling. Input transversity distributions are obtained by saturating the Soffer inequality at a low hadronic mass scale. Results for the polarized BNL-RHIC proton-proton collider and the proposed HERA-N fixed-target experiment are presented, and the influence of the limited muon acceptance of the detectors on measurements of the asymmetry is studied in detail.
We propose two new observables to measure the charge asymmetry in hadronic top-quark pair production in association with a hard jet. The incline asymmetry, based on the inclination between the planes of initial- and final-state momenta, probes the charge asymmetry in the quark-antiquark channel. Compared to the hitherto investigated rapidity asymmetries, the incline asymmetry provides improved access to the partonic charge asymmetry at both the Tevatron and the LHC. The energy asymmetry, based on the energy difference between top and antitop quarks, for the first time allows us to probe the ch…
Probing the Moderate-to-Large-$x$ Gluon Helicity with $J/ψ$ Production at $\sqrt{s}=\mathrm{GeV}$
Moscow Institute of Physics and Technology（莫斯科物理技术学院）；Joint Institute for Nuclear Research（苏联联合核研究所）；Institute for Nuclear Physics, Almaty（阿拉木图核物理研究所）；Institute of Physics, Academia Sinica（中央研究院物理学研究所）；Computational Theoretical High Energy Physics Lab, Department of Physics, Doaba College（多巴学院物理系计算理论高能物理实验室）；Computational High Energy Physics Lab, Department of Physics, Dr. B.R. Ambedkar National Institute of Technology（B.R.安贝德卡尔国立理工学院物理系计算高能物理实验室）
The rapidity dependent directed flow of particles produced in a relativistic heavy ion collision can be generated in the hydrodynamic expansion of a tilted source. The asymmetry of the pressure leads to a build up of a directed flow of matter with respect to the collision axis. The experimentally observed ordering of the directed flow of baryons, pions and antibaryons can be described as resulting from the expansion of a baryon inhomogeneous fireball. An uneven distribution of baryons in the transverse plane leads to an asymmetry in the collective push for protons and antiprotons. Precise meas…
We consider the production of W bosons in hadron collisions, and the subsequent leptonic decay W->lnu_l. We study the asymmetry between the rapidity distributions of the charged leptons, and we present its computation up to the next-to-next-to-leading order (NNLO) in QCD perturbation theory. Our calculation includes the dependence on the lepton kinematical cuts that are necessarily applied to select W-> lnu_l events in actual experimental analyses at hadron colliders. We illustrate the main differences between the W and lepton charge asymmetry, and we discuss their physical origin and the effe…
This is the summary report of the Top Quark Kinematics working group prepared for Snowmass 2013. We survey the current state of theoretical predictions for top pair differential distributions, in both boosted and un-boosted regimes, and present an overview of uncertainties and prospects for top spin correlations. We study the prospects for measuring the inclusive SM top pair production asymmetry AFC at LHC 14 as a function of systematic error, and show that some improvement over current systematic uncertainties, as customarily handled, is required for observing a SM-size asymmetry. Cuts on top…
The rapidity-even dipolar flow v1 associated with dipole asymmetry in the initial geometry is measured over a broad range in transverse momentum 0.5 GeV<pT<9 GeV, and centrality (0-50)% in Pb-Pb collisions at sqrt(s_NN)=2.76 TeV, recorded by the ATLAS experiment at the LHC. The v1 coefficient is determined via a two-component fit of the first order Fourier coefficient, v_{1,1}= cos Δϕ, of two-particle correlations in azimuthal angle Δϕ=ϕ_a-ϕ_b as a function of pT^a and pT^b. This fit is motivated by the finding that the pT dependence of v_{1,1}(pT^a,pT^b) data are consistent with the combined …
The top quark forward-backward asymmetry measured at the Tevatron collider shows a large deviation from standard model expectations. Among possible interpretations, a non-universal $Z^\prime$ model is of particular interest as it naturally predicts a top quark in the forward region of large rapidity. To reproduce the size of the asymmetry, the couplings of the $Z^\prime$ to standard model quarks must be large, inevitably leading to copious production of same-sign top quark pairs at the energies of the Large Hadron Collider (LHC). We explore the discovery potential for $tt$ and $ttj$ production…
We consider the recent measurement of the top quark forward-backward asymmetry at the Fermilab Tevatron, which shows a discrepancy of slightly more than 2$σ$ compared to the SM prediction. We find that $t$-channel exchange of a color sextet or triplet scalar particle can explain the measurement, while leaving the cross section for $t \bar{t}$ production within measured uncertainties. Such particles have good discovery prospects by study of the kinematic structure of $t \bar{t}$+jets at the LHC.
Experimental data at RHIC and SPS energies suggest a systematic correlation between yield ratio $\bar{p}/p$ and $K^{-}/K^{+}$, which reveal some universality of hadron production in relativistic heavy ion collisions. We propose an explanation based on the quark combination mechanism in which the production asymmetry between baryons and antibaryons is focused on especially. We start from the basic ideas of quark combination to carry out a general analysis of the properties of the global production of baryons and mesons and obtain the yields of baryons, antibaryons and mesons as functions of the…
In this paper we propose to investigate the transverse single spin asymmetry in the inelastic $J/Ψ$ photoproduction in $p^\uparrow p$ and $p^\uparrow A$ collisions at RHIC energies. At leading order this process probes the gluon Sivers function. We predict large values for the cross sections, which indicates that its experimental analysis is, in principle, feasible. The rapidity dependence of the single spin asymmetry is presented. We obtain that the asymmetry is strongly dependent on the model used for the gluon Sivers function and that it can be probed by the analysis of the $J/Ψ$ production…
A study on the prompt photon production within the QCD color dipole picture with emphasis in $pp$ and $pA$ collisions at the LHC energy regimes is performed. We present predictions for the differential cross section as a function of photon transverse momentum at different rapidity bins considering updated phenomenological color dipole models, which take into account the QCD gluon saturation physics. The results are directly compared to the recent experimental measurements provided by CMS and ATLAS Collaborations, showing a reasonable agreement in all rapidity bins with no free parameters. Spec…
A large forward-backward asymmetry is seen in both the top quark rapidity distribution $A_{FB}^t$ and in the rapidity distribution of charged leptons $A_{FB}^\ell$ from top quarks produced at the Tevatron. We study the kinematic and dynamic aspects of the relationship of the two observables arising from the spin correlation between the charged lepton and the top quark with different polarization states. We emphasize the value of both measurements, and we conclude that a new physics model which produces more right-handed than left-handed top quarks is favored by the present data.
