We explore the system size dependence of heavy-quark-QGP interaction by studying the heavy flavor meson suppression and elliptic flow in Pb-Pb, Xe-Xe, Ar-Ar and O-O collisions at the LHC. The space-time evolution of the QGP is simulated using a (3+1)-dimensional viscous hydrodynamic model, while the heavy-quark-QGP interaction is described by an improved Langevin approach that includes both collisional and radiative energy loss inside a thermal medium. Within this framework, we provides a reasonable description of the $D$ meson suppression and flow coefficients in Pb-Pb collisions, as well as predictions for both $D$ and $B$ meson observables in other collision systems yet to be measured. We find a clear hierarchy for the heavy meson suppression with respect to the size of the colliding nuclei, while their elliptic flow coefficient relies on both the system size and the geometric anisotropy of the QGP. Sizable suppression and flow are predicted for both $D$ and $B$ mesons in O-O collisions, which serve as a crucial bridge of jet quenching between large and small collision systems. Scaling behaviors between different collision systems are shown for heavy meson suppression factor and the bulk-eccentricity-rescaled heavy meson elliptic flow as functions of the number of participant nucleons in heavy-ion collisions.
The role of hadronic matter in the suppression of open heavy flavored mesons has been studied. The heavy-quarks (HQs) suppression factors have been calculated and contrasted with the experimental data obtained from nuclear collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadronic Collider (LHC) experiments. It is found that the suppression in the hadronic phase at RHIC energy is around $20%-25%$ whereas at the LHC it is around $10%-12%$ for the D meson. In case of B meson the hadronic suppression is around $10%-12%$ and $5%-6%$ at RHIC and LHC energies respectively. Present study…
Suppressions of light and heavy flavor observables are considered to be excellent probes of QCD matter created in ultra-relativistic heavy ion collisions. Suppression predictions of quark and gluon jets appear to suggest a clear hierarchy according to which neutral pions should be more suppressed than D mesons, which in turn should be more suppressed than single electrons. However, joint comparison of neutral pion (light probe) and non-photonic single electron (heavy probe) suppression data at RHIC unexpectedly showed similar jet suppression for these two probes, which presents the well-known …
In this paper we consider the suppression of bottomonium states in ultrarelativistic heavy ion collisions. We compute the suppression as a function of centrality, rapidity, and transverse momentum for the states Upsilon(1s), Upsilon(2s), Upsilon(3s), chi_b1, and chi_b2. Using this information, we then compute the inclusive Upsilon(1s) suppression as a function of centrality, rapidity, and transverse momentum including feed down effects. Calculations are performed for both RHIC sqrt(s_NN)=200 GeV Au-Au collisions and LHC sqrt(s_NN)=2.76 TeV Pb-Pb collisions. From the comparison of our theoretic…
The approach to problem of nuclear shadowing based on Gribov Reggeon calculus is presented. Here the total cross section of $h A$ interaction is found in a parameter-free description, employing the new data on the gluon density of the Pomeron, measured with high precision at HERA, as input. The model is then applied for calculation of $J/ψ$ production in $d Au$ collisions at top RHIC energy. It is shown that the theoretical estimates are in a very good agreement with the PHENIX data, and further predictions for the $J/ψ$ suppression in $p Pb$ collisions at coming soon LHC are made.
The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark-gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed in…
Recent measurements of the proton to pion ratio at $\sqrt{s}_{NN}=2.7$ TeV by the ALICE collaboration at the LHC have found it to be lower than predictions from thermal fits. In this paper we investigate the role that the extended mass spectrum via Hagedorn states- massive resonances that follow an exponential mass spectrum and possess large decay widths- play in the determination of particle ratios at LHC through a scenario of multi-particle reactions and dynamical chemical equilibrium within the hadron gas phase. We show that it is possible to describe the lower $p/π$ ratio at LHC while stil…
Both charged hadrons and D mesons are considered to be excellent probes of QCD matter created in ultra relativistic heavy ion collisions. Surprisingly, recent experimental observations at LHC show the same jet suppression for these two probes, which - contrary to pQCD expectations - may suggest similar energy losses for light quarks and gluons in QCD medium. We here use our recently developed energy loss formalism in a finite size dynamical QCD medium to analyze this phenomenon that we denote as the "heavy flavor puzzle at LHC". We show that this puzzle is a consequence of an unusual combinati…
We perform a joint jet tomographic analysis of the data on the nuclear modification factor $R_{AA}$ from PHENIX at RHIC and ALICE at LHC. The computations are performed accounting for radiative and collisional parton energy loss with running coupling constant. Our results show that the observed slow variation of $R_{AA}$ from RHIC to LHC indicates that the QCD coupling constant is suppressed in the quark-gluon plasma produced at LHC.
Jet suppression of light and heavy flavor observables is considered to be an excellent tool to study the properties of QCD matter created in ultra-relativistic heavy ion collisions. We calculate the suppression patterns of light hadrons, D mesons, non-photonic single electrons and non-prompt $J/ψ$ in Pb+Pb collisions at LHC. We use a theoretical formalism that takes into account finite size {\it dynamical} QCD medium with finite magnetic mass effects and running coupling, which is integrated into a numerical procedure that uses no free parameters in model testing. We obtain a good agreement wi…
We suggest that the combined effect of screening, gluon-induced dissociation, collisional damping, and reduced feed-down explains most of the sequential suppression of Upsilon(nS) states that has been observed in PbPb relative to pp collisions at sqrt(s_NN) = 2.76 TeV. The suppression is thus a clear, albeit indirect, indication for the presence of a QGP. The Upsilon(1S) ground state suppression is essentially due to reduced feed-down, collisional damping and gluodissociation, whereas screening prevails for the suppression of the excited states.
We calculate open heavy-flavor (HF) transport in relativistic heavy-ion collisions by applying a strong-coupling treatment in both macro- and microscopic dynamics (hydrodynamics and non-perturbative diffusion interactions). The hydrodynamic medium evolution is quantitatively constrained by bulk and multi-strange hadron spectra and elliptic flow. The heavy quark (HQ) transport coefficient is evaluated from a non-perturbative $T$-matrix approach in the Quark-Gluon Plasma (QGP) which, close to the critical temperature, leads to resonance formation and feeds into the recombination of heavy quarks …
I compute the thermal suppression of the Upsilon(1s) and chi_b1 states in sqrt(s_NN)=2.76 TeV Pb-Pb collisions. Using the suppression of each of these states I estimate the total R_AA for the Upsilon(1s) state as a function of centrality, rapidity, and transverse momentum. I find less suppression of the chi_b1 state than would be traditionally assumed; however, my final results for the total Upsilon(1s) suppression are in good agreement with recent preliminary CMS data.
The nuclear modification factor R_AA for charged hadron production at the LHC is predicted from jet energy loss induced by gluon bremsstrahlung. The Arnold, Moore, and Yaffe formalism is used, together with an ideal hydrodynamical model.
A parameter-free calculation for J/Psi suppression in pA collisions, based on the dipole description, is confronted with the new data from the PHENIX experiment. Achieving good agreement, we employed this model predicting the contribution of initial state interactions (ISI) to J/Psi suppression in AA collisions. Such a transition from pA to AA is not straightforward, since involves specific effects of double color filtering and boosting of the saturation scale. Relying on this refined ISI contribution, we updated the previous analysis of RHIC data on J/Psi production in Cu-Cu and Au-Au collisi…
A new Monte Carlo model of jet quenching in nuclear collisions, CUJET1.0, is applied to predict the jet flavor dependence of the nuclear modification factor for fragments {\it $f=π,D,B,e^-$} from quenched jet flavors {\it $g,u,c,b$} in central collisions at RHIC and LHC. The nuclear modification factors for different flavors are predicted to exhibit a novel level crossing pattern over a transverse momentum range $5< p_T< 100$ GeV which can test jet-medium dynamics in quark gluon plasmas.
Using the color glass condensate formalism, we study the nuclear modification of forward $J/ψ$ and $D$ meson production in high energy proton-nucleus collisions at the LHC. We show that relying on the optical Glauber model to obtain the dipole cross section of the nucleus from the one of the proton fitted to HERA DIS data leads to a smaller nuclear suppression than in the first study of these processes in this formalism and a better agreement with experimental data.
Nuclear modification factor $R_{AA}(p_{T})$ for large transverse momentum pion spectra in $Pb+Pb$ collisions at $\sqrt{s}=2.76$ TeV is predicted within the NLO perturbative QCD parton model. Effect of jet quenching is incorporated through medium modified fragmentation functions within the higher-twist approach. The jet transport parameter that controls medium modification is proportional to the initial parton density and the coefficient is fixed by the RHIC data on suppression of large $p_{T}$ hadron spectra. Data on charged hadron multiplicity $dN_{ch}/dη=1584 \pm 80$ in central $Pb+Pb$ colli…
We discuss a number of cold nuclear matter effects that can modify open heavy flavor and quarkonium production in proton-nucleus collisions and could thus also affect their production in nucleus-nucleus collisions, in addition to hot quark-gluon plasma production. We show some results for $p+$Pb collisions at sqrt s = 5 TeV at the LHC.
The strong suppression of heavy quarkonia is a good indicator that one has generated a quark-gluon plasma (QGP) in an ultrarelativistic heavy ion collision. Recent advancements in first principles calculations of the heavy quark potential provide additional insight into this suppression and can be used to further pin down the in-medium properties of the QGP. Realistic 3+1d dissipative hydrodynamical models can be used to simulate the QGP and, with bottomonium as a probe, one can make inferences for the initial temperature of the QGP and other phenomenological parameters such as the shear visco…
We examine whether it is possible to simultaneously describe the experimental data from RHIC and LHC on nuclear suppression of light hadrons and non-photonic single electrons in the pQCD picture of parton energy loss. We perform calculations accounting for both radiative and collisional energy loss. We show that once the coupling constant is fixed from comparison with data on the nuclear modification factor for light hadrons it gives a satisfactory agreement with data on the electron R_{AA} and azimuthal anisotropy v_2. Our results show that the collisional mechanism is only of marginal signif…
High momentum hadron suppression is considered to be an excellent probe of jet-medium interactions in QCD matter created in ultra-relativistic heavy ion collisions. We previously showed that our dynamical energy loss formalism can accurately explain suppression measurements at 200 GeV Au+Au collisions at RHIC and 2.76 TeV Pb+Pb collisions at the LHC. With the upcoming LHC measurements at notably higher collision energies, there is a question of what differences, with respect to the current (2.76 TeV) measurements, can be expected. In this paper we concentrate on heavy flavor suppression at the…
The stochastic dynamics of c and b quarks in the fireball created in nucleus-nucleus collisions at RHIC and LHC is studied employing a relativistic Langevin equation, based on a picture of multiple uncorrelated random collisions with the medium. Heavy-quark transport coefficients are evaluated within a pQCD approach, with a proper HTL resummation of medium effects for soft scatterings. The Langevin equation is embedded in a multi-step setup developed to study heavy-flavor observables in pp and AA collisions, starting from a NLO pQCD calculation of initial heavy-quark yields, complemented in th…
The long life-time of the quark-gluon plasma likely to be created in the relativistic heavy ion collisions at RHIC and LHC energies renders it sensitive to the details of the equation of state of the quark-matter. We show that the $p_T$ dependence of the survival probability of the directly produced $J/ψ$ at RHIC energies and that of the directly produced $Υ$ at LHC energies is quite sensitive to the speed of sound in the quark matter, which relates the pressure and the energy density of the plasma. The transverse expansion of the plasma is shown to strongly affect the $J/ψ$ suppression at LHC…
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/π 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.
We explore the possibility that the masses for the first two generations of fermions and the quark flavor violation are generated radiatively in the Minimal Supersymmetric Standard Model. We assume that the source of all flavor violation resides in the the supersymmetry breaking sector and is transmitted radiatively to the Standard Model fermion sector through finite corrections at low energy. The approximate radiative alignment between the Yukawa and soft supersymmetry breaking matrices helps to suppress some of the supersymmetric contributions to flavor changing processes, overcoming current…
We present our predictions on multiplicities and $J/ψ$ suppression at LHC energies. Our results take into account shadowing effects in the initial state and final state interactions with the hot medium. We obtain 1800 charged particles at LHC and the $J/ψ$ suppression increases by a factor 5 to 6 compared to RHIC.
We present the reweighting of two sets of nuclear PDFs, nCTEQ15 and EPPS16, using a selection of experimental data on heavy-flavor meson [D0, J/psi, J/psi from B and Upsilon(1S)] production in proton-lead collisions at the LHC which were not used in the original determination of these nuclear PDFs. The reweighted PDFs exhibit significantly smaller uncertainties thanks to these new heavy-flavor constraints. We present a comparison with another selection of data from the LHC and RHIC which were not included in our reweighting procedure. The comparison is overall very good and serves as a validat…
In this work, we calculate energy loss of heavy quark (charm and bottom) due to elastic collisions and gluon radiation in hot/dense medium. The collisional energy loss has been obtained using QCD calculations. The radiative energy loss is calculated using reaction operator formalism and generalized dead cone approach. We rederive the energy loss expression using same assumptions as generalized dead cone approach but obtain slightly different results. We also improve the model employed to calculate path length and the system evolution. The nuclear modification factors $R_{AA}$ including shadowi…
Recent experiments have observed large anisotropic collective flows in high multiplicity proton-lead collisions at the Large Hadron Collider (LHC), which indicates the possible formation of mini quark-gluon plasma (QGP) in small collision systems. However, no jet quenching has been confirmed in such small systems so far. To understand this intriguing result, the system size scan experiments have been proposed to bridge the gap between large and small systems. In this work, we perform a systematic study on both heavy and light flavor jet quenching in different collision systems at the LHC energ…
Reliable predictions for jet quenching in ultra-relativistic heavy ion collisions require accurate computation of radiative energy loss. While all available energy loss calculations assume zero magnetic mass, in accordance with the one-loop perturbative calculations, different non-perturbative approaches report a non-zero magnetic mass at RHIC and LHC. We generalized the dynamical energy loss formalism, to consistently include a possibility for existence of non-zero magnetic screening. We show that this generalization indicates a fundamental constraint on electric to magnetic mass ratio, which…
We show that we can reproduce all the features of bottomonium suppression in both proton-nucleus and nucleus-nucleus collisions at LHC energies in a comover-interaction picture. For each collisions system, we use the measured {\it relative} suppression of the excited $Υ$(2S) and $Υ$(3S) states to $Υ$(1S) by ATLAS and CMS to parametrise the scattering cross sections of all $S$- and $P$-wave bottomonia with the comoving particles created during the collisions. In addition to a single nonpertubative parameter, these cross sections depend on the momentum distribution of these comovers which we fou…
We here concentrate on available $π^\pm$ and $K^\pm$ ALICE preliminary $R_{AA}$ data in central 2.76 TeV Pb+Pb collisions at LHC. These data show an interesting fine resolution hierarchy, i.e. the measured $K^\pm$ data have consistently lower suppression compared to $π^\pm$ measurements. We here ask whether theoretical predictions based on energy loss in dynamical QCD medium can quantitatively and qualitatively explain such fine resolution. While our suppression calculations agree well with the data, we find that qualitatively explaining the fine hierarchy critically depends on the choice of f…
Understanding properties of QCD matter created in ultra-relativistic heavy-ion collisions is a major goal of RHIC and LHC experiments. An excellent tool to study these properties is jet suppression of light and heavy flavor observables. Utilizing this tool requires accurate suppression predictions for different experiments, probes and experimental conditions, and their unbiased comparison with experimental data. With this goal, we here extend our dynamical energy loss formalism towards generating predictions for non-central collisions; the formalism takes into account both radiative and collis…
Models of minimal lepton flavor violation where the seesaw scale is higher than the relevant flavor scale predict that all lepton flavor violation is proportional to the charged lepton Yukawa matrix. If extra vector-like leptons are within the reach of the LHC, it will be possible to test the resulting predictions in ATLAS/CMS.
We show that in supersymmetric models with explicit flavor lepton number violation due to soft supersymmetry breaking mass terms there could be detectable flavor lepton number violation in slepton decays. We estimate LHC discovery potential of the lepton flavor number violation in slepton decays.
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…
Jet suppression is considered to be an excellent probe of QCD matter created in ultra-relativistic heavy ion collisions. Our theoretical predictions of jet suppression, which are based on our recently developed dynamical energy loss formalism, show a robust agreement with various experimental data, which spans across different probes, experiments (RHIC and LHC) and experimental conditions (i.e. all available centrality regions). This formalism includes several key ingredients, such as inclusion of dynamical scattering centers, finite size QCD medium, collisional energy loss, finite magnetic ma…
Jet Flavor Tomography is a powerful tool used to probe the properties of Quark Gluon Plasma formed in heavy ion collisions at RHIC and LHC. A new Monte Carlo model of jet quenching developed at Columbia University, CUJET, was applied to predict the jet flavor and centrality dependence of the nuclear modification factor $R_{AA}$. The predictions for fragments $f=π,D,B,e$, derived from quenched jet flavors $a=g,u,c,b$ in central and peripheral collisions at RHIC and LHC, exhibit novel features such as a level crossing pattern in $R_{AA\rightarrow a\rightarrow f}$ over a broad transverse momentum…
Motivated by the null results of LHC searches, which together with the Higgs mass, severely constrain minimal supersymmetric extensions of the standard model, we adopt a model-independent approach to study charged slepton flavor. We examine a number of simplified models, with different subsets of sleptons, electroweak gauginos, and Higgsinos, and derive the allowed slepton flavor dependence in the region probed by current LHC searches, and in the region relevant for the 14 TeV LHC. We then study the impact of the allowed flavor dependence on lepton plus missing energy searches. In some cases, …
We substantially refine our previously developed model for the suppression of Upsilon mesons in the quark-gluon plasma (QGP) formed in 2.76 TeV PbPb collisions at the LHC. It accounts for gluodissociation of the six bottomium states Y(nS), chi_b(nP) with n = 1,2,3, collisional damping of these states as described in a complex potential, screening of the real part of the potential, and the subsequent decay cascade. In the hydrodynamical calculation of the expanding fireball, we take into account the effect of transverse expansion on the suppression factors, and finite transverse momenta of the …
The mixing between third and second (or first) generation squarks is very small in supersymmetric models with minimal flavor violation such as gauge-, anomaly- or gaugino-mediation. An opportunity to measure this mixing will arise if the lightest stop is close enough in mass to the lightest neutralino, so that the decays into third generation quarks are kinematically forbidden. We analyze under which circumstances it might become possible to measure at the Large Hadron Collider (LHC) the rate of the flavor changing stop decays.
We discuss the production of $D$-mesons and $J/ψ$ in high multiplicity proton-proton and proton-nucleus collisions within the Color-Glass-Condensate (CGC) framework. We demonstrate that the modification of the LHC data on $D$ and $J/ψ$ yields in high multiplicity events relative to minimum bias events arise from a significant enhancement of the gluon saturation scales of the corresponding rare parton configurations in the colliding protons and nuclei. For a given event multiplicity, we predict these relative yields to be energy independent from $\sqrt{s}=200$ GeV at RHIC to the highest LHC ene…
A new process with the lepton flavor violation (LFV) is presented in the setup for LHC. The LFV is induced by the one-loop effect through Higgs bosons in the framework of the type-III two Higgs doublet model. It is demonstrated that the vast of parameter space in the Yukawa sector could be accessed by current and future LHC experiments.
Some of the open questions on jet quenching are expected to be clarified by measuring heavy-flavored mesons at high transverse momentum. The formalism based on radiative in-medium energy-loss, which describes other high-pt results at RHIC, gives definite predictions for the suppression of charm and beauty quarks. However, the uncertainties from both contributions to the observed electrons make the interpretation of the data difficult due to the absence of a well calibrated benchmark. We review the present situation as well as the consequences for the future LHC. We also comment on the use of h…
Recent results from Super Kamiokande suggest $ν_μ-ν_τ$ mixing and hence lepton flavor violation. In supersymmetric models, this flavor violation may have implications for the pattern of slepton masses and mixings. Possible signals for this mixing in the decays of sleptons produced at the LHC are discussed. The sensitivity expected is compared to that of rare decays such as $τ\to μγ$.
The physics underlying quark and lepton masses and mixings (the "flavor problem") is the least well understood aspect of the Standard Model. Some questions of flavor physics, and ways in which the LHC can help shed light on this problem, are described.
We examine the rates for the production of black holes(BH) at the LHC in light of the exponential suppression of the geometric cross section estimate recently proposed by Voloshin. We show that the resulting production rates will still be quite large over a reasonably wide range of model parameters. While BH production may no longer be the dominant collider process, its unique signature will ensure observability over more conventional backgrounds.
We consider the possibility that dark matter can communicate with the Standard Model fields via flavor interactions. We take the dark matter to belong to a "dark sector" which contains at least two types, or "flavors", of particles and then hypothesize that the Standard Model fields and dark matter share a common interaction which depends on flavor. As, generically, interaction eigenstates and mass eigenstates need not coincide, we consider both flavor-changing and flavor-conserving interactions. These interactions are then constrained by meson decays, kaon mixing, and current collider bounds,…
In a generic supersymmetric extension of the Standard Model, there will be lepton flavor violation at a neutral gaugino vertex due to misalignment between the lepton Yukawa couplings and the slepton soft masses. Sleptons produced at the LHC through the cascade decays of squarks and gluinos can give a sizable number of events with 4 leptons. This channel could give a clean signature of supersymmetric lepton flavor violation under conditions which are identified.
We show that we can reach a global and coherent description of bottomonium suppression in both proton-nucleus and nucleus-nucleus collisions at the LHC energies. The measured relative suppression of the excited bottomonium states as compared to their ground state allows us to constrain the scattering cross sections between the bottomonia and the comovers created during the collisions. Our result hints at a similar energy distribution of these comovers in the environment created by proton-nucleus and nucleus-nucleus collisions. Along the way of our study, we also update our knowledge for the bo…
The suppression and collective flow of open and hidden heavy flavor in ultra-relativistic heavy ion collisions is studied with the partonic transport model Boltzmann Approach to MultiParton Scatterings (BAMPS). Charm and bottom quarks interact with the rest of the medium via elastic scatterings with an improved Debye screening and a running coupling. Heavy flavor electron data from RHIC can only be described if the cross section is multiplied with K=3.5 to mimic the contribution from radiative processes. With the same value for K we compare to elliptic flow data of D mesons at the LHC and find…
In supersymmetric scenarios, the seesaw mechanism involving heavy right-handed neutrinos implies sizable lepton flavor violation (LFV) in the slepton sector. We discuss the potential of detecting LFV processes at the LHC in mSUGRA+seesaw scenarios and for general mixing in either the left- or right-handed slepton sector. The results are compared with the sensitivity of rare LFV mu -> e gamma decay experiments.
We show that the discovery channel for dark matter (DM) production at colliders can be through flavor violating interactions resulting in a novel signature of a single top and large missing transverse energy. We discuss several examples where the production of DM is dominated by flavor violating couplings: minimal flavor violating models with a large bottom Yukawa, models with horizontal symmetries, and DM in nontrivial flavor group representations. Discovery at the 7 TeV LHC with a few fb^-1 may already be possible.
We present an analysis of data on light flavour hadron production as function of event multiplicity at LHC energies measured by the ALICE collaboration. The strangeness-canonical approach within the framework of the THERMUS statistical hadronisation model is used for a simultaneous description of pp, p-Pb, and Pb-Pb collisions. The rapidity window dependence of the strangeness correlation volume is addressed and a value of $Δy = 1.33 \pm 0.28$ is found. With the exception of the $ϕ$-meson, an excellent description of the experimental data is found.
We examine the flavor dependence of the nuclear modification factor $R_{AA}$ in the pQCD calculations at LHC energies. The computations are performed accounting for radiative and collisional parton energy loss with running coupling constant. Our results show that the recent LHC data on the $R_{AA}$ for charged hadrons, D-mesons and non-photonic electrons agree reasonably with the pQCD picture of the parton energy loss with the dominating contribution from the radiative mechanism.
We discuss the interplay of screening, absorption and regeneration effects, on the quantum mechanical evolution of quarkonia states, within a time-dependent harmonic oscillator (THO) model with complex oscillator strength. We compare the results with data for R_AA/R_AA(CNM) from CERN and RHIC experiments. In the absence of a measurement of cold nuclear matter (CNM) effects at LHC we estimate their role and interpret the recent data from the ALICE experiment. We also discuss the temperature dependence of the real and imaginary parts of the oscillator frequency which stand for screening and abso…
We present a modified colour screening model for $J/ψ$ suppression in the Quark-Gluon Plasma (QGP) using quasi-particle model (QPM) as equation of state (EOS). Other theoretical ingredients incorporated in the model are feed-down from higher resonances namely, $χ_c$, and $ψ^{'}$, dilated formation time for quarkonia and viscous effects of the QGP medium. Assuming further that the QGP is expanding with Bjorken's hydrodynamical expansion, the present model is used to analyze the centrality dependence of the $J/ψ$ suppression in mid-rapidity region and compare it with the data obtained from SPS, …
We consider the top forward-backward (FB) asymmetry at the Tevatron and top charge asymmetry at the LHC within chiral U(1)^\prime models with flavor-dependent U(1)^\prime charges and flavored Higgs fields, which were introduced in the ref. [65]. The models could enhance not only the top forward-backward asymmetry at Tevatron, but also the top charge asymmetry at LHC, without too large same-sign top pair production rates. We identify parameter spaces for the U(1)^\prime gauge boson and (pseudo)scalar Higgs bosons where all the experimental data could be accommodated, including the case with abo…
Quarkonium production in proton-nucleus collisions is a powerful tool to disentangle cold nuclear matter effects. A model based on coherent energy loss is able to explain the available quarkonium suppression data in a broad range of rapidities, from fixed-target to collider energies, suggesting cold energy loss to be the dominant effect in quarkonium suppression in p-A collisions. This could be further tested in a high-energy fixed-target experiment using a proton or nucleus beam. The nuclear modification factors of J/$ψ$ and $Υ$ as a function of rapidity are computed in p-A collisions at $\sq…
