We single out the role of fully coherent induced gluon radiation on light hadron production in pA collisions. The effect has an interesting color structure, as the induced radiation depends on the global color charge of the partonic subprocess final state. Baseline predictions for light hadron nuclear suppression in pPb collisions at the LHC are provided, taking into account only the effect of fully coherent energy loss, which proves of the same order of magnitude as gluon shadowing or saturation. This underlines the need to include fully coherent energy loss in phenomenological studies of hadron production in pA collisions.
The method to simulate the rescattering and energy loss of hard partons in ultrarelativistic heavy ion collisions has been developed. The model is a fast Monte-Carlo tool introduced to modify a standard PYTHIA jet event. The full heavy ion event is obtained as a superposition of a soft hydro-type state and hard multi-jets. The model is applied to analysis of the jet quenching pattern at RHIC.
Recently an improved quenching factor (QF) measurement for low-energy nuclear recoils in CsI[Na] has been reported by the COHERENT Collaboration. The new energy-dependent QF is characterized by a reduced systematic uncertainty and leads to a better agreement between the experimental COHERENT data and the Standard Model (SM) expectation. In this work, we report updated constraints on parameters that describe the process of coherent elastic neutrino-nucleus scattering within and beyond the SM, and we also present how the new QF affects their interpretation.
Using the Fokker-Planck equation we have studied the drag co-efficient $A(t)$ and the consequent shift $Δp_\perp (L)$ in the transverse momentum due to collisional energy loss of energetic partons while passing through a chemically equilibrating quark-gluon plasma. Based on these we estimate the quenching factor $Q(p_\perp)$ when the medium is undergoing longitudinal expansion governed by master rate equations. In contrast to the case of chemically equilibrated plasma investigated earlier by Mustafa and Thoma \cite{mus} we find less quenching because our calculated $Q(p_\perp)$ is always great…
Typically the materialization of high energetic transverse partons to hadronic jets is assumed to occur outside the reaction zone in a relativistic heavy ion collision. In contrast, a quantum mechanical estimate yields a time on the order of only a few fm/c for building up the hadronic wavefunction for jets with typical transverse momenta of pT < 10 GeV as accessible at RHIC facilities. The role of possible elastic or inelastic collisions of these high pT particles with the bulk of hadrons inside the fireball is addressed by means of an opacity expansion in the number of collisions. This analy…
The multiple scatterings incurred by a hard quark produced in a nuclear medium induce the emission of soft gluons which carry a fraction of the quark energy and eventually affect the hadronization process. Here, the depletion of semi-inclusive hadron spectra in DIS on various nuclei (N, Ne, Cu, Kr) is computed as a function of nu and z to leading order in alpha_s through medium-modified fragmentation functions. Using the transport coefficient q previously determined from Drell-Yan production, the predictions are found to be in good agreement with EMC and HERMES preliminary data. Calculations o…
The inclusive transverse momentum (pt) distribution of hadrons inside jets produced in PbPb and pp collisions are simulated with the YaJEM and Pythia 6 Monte Carlo (MC) event generators. The effects of jet quenching are studied via the ratios of PbPb over pp hadron pt spectra, either by accounting for the induced virtuality Delta Q^2 transferred from the strongly-interacting medium to the parton shower or by modifying the soft sector of the parton-to-hadron fragmentation functions. The MC results are compared to experimental jet data measured by the CMS experiment at a center-of-mass energy of…
We present a model for radiative energy loss of heavy quarks in quark gluon plasma which incorporates coherence effects. We then study its consequences on the radiation spectra as well as on the nuclear modification factor of open heavy mesons produced in ultrarelativistic heavy ion collisions.
We estimate the energy loss distribution and investigate the quenching of hadron spectra in ultrarelativistic heavy-ion collisions due to the collisional energy loss of energetic partons from hard parton collisions in the initial stage.
Theoretical understanding of the observed jet quenching measurements at RHIC and LHC is challenging in QCD because it requires understanding of parton to hadron fragmentation function in non-equilibrium QCD. In this paper, by using closed-time path integral formalism, we derive the gauge invariant definition of the gluon to hadron fragmentation function in non-equilibrium QCD which is consistent with factorization theorem in non-equilibrium QCD from first principles.
Within a hadron-string dynamical transport approach (HSD) we investigate the attenuation of high transverse momentum ($\pT$) hadrons as well as the suppression of 'near-side' and 'far-side' jets in $Au+Au$ collisions at invariant energies $\sqrt{s}$ = 200 GeV and $\sqrt{s}$ = 62.4 GeV in comparison to the data available from the Relativistic Heavy-Ion Collider (RHIC). From our transport studies we find that a significant part of the high $\pT$ hadron attenuation seen experimentally can be attributed to inelastic interactions of 'leading' pre-hadrons with the dense hadronic environment. In addi…
We determine how the yield of large transverse momentum hadrons is modified due to induced gluon radiation off a hard parton traversing a QCD medium. The quenching factor is formally a collinear- and infrared-safe quantity and can be treated perturbatively. In spite of that, in the $p_\perp$ region of practical interest, its value turns out to be extremely sensitive to large distances and can be used to unravel the properties of dense quark-gluon final states produced in heavy ion collisions. We also find that the standard modelling of quenching by shifting $p_\perp$ in the hard parton cross s…
We compare fully perturbative and fully nonperturbative pictures of high-pT energy loss calculations to the first results from LHC. While over-suppressed compared to published ALICE data, parameter-free pQCD predictions based on the WHDG energy loss model constrained to RHIC data simultaneously describe well the preliminary CMS hadron suppression, ATLAS charged hadron v2, and ALICE D meson suppression; we also provide for future reference WHDG predictions for B meson RAA. However, energy loss calculations based on AdS/CFT also qualitatively describe well the RHIC pion and non-photonic electron…
The recent developments on PYQUEN, HYDJET and HYDJET++ event generators are presented. The partonic energy loss model PYQUEN is implemented as the modification of the "standard" jet event obtained with the generator of hadron-hadron interactions PYTHIA. HYDJET and HYDJET++ are the Monte-Carlo event generators for the simulation of relativistic heavy ion AA collisions considered as a superposition of the soft, hydro-type state and the hard, multi-parton fragmentation. HYDJET++ model is the development and continuation of HYDJET generator, and it includes more detailed treatment of the "thermal"…
Significant jet quenching in central $Au+Au$ collisions has been discovered at RHIC. This paper provides theoretical arguments and lists experimental evidence that the observed jet quenching at RHIC is due to parton energy loss instead of hadron rescattering or absorption in a hadronic medium. These include: (1) hadron formation time based on the uncertainty principle, (2) $p_T$ dependence and (3) centrality dependence of the observed jet quenching, (4) jet-like leading hadron correlations (5) high-$p_T$ azimuthal anisotropy and (6) experimental data from $Pb+Pb$ collisions at SPS and $e+A$ co…
Hadron production in semi-inclusive deep-inelastic scattering of leptons from nuclei is an ideal tool to determine and constrain the transport coefficient in cold nuclear matter. The leading-order computations for hadron multiplicity ratios are performed by means of the SW quenching weights and the analytic parameterizations of quenching weights based on BDMPS formalism. The theoretical results are compared to the HERMES positively charged pions production data with the quarks hadronization occurring outside the nucleus. With considering the nuclear geometry effect on hadron production, our pr…
The first LHC data on high transverse momentum hadron and dijet spectra in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed in the frameworks of PYQUEN jet quenching model. The presented studies for the nuclear modification factor of high-pT hadrons and the imbalance in dijet transverse energy support the supposition that the intensive wide-angular ("out-of-cone") medium-induced partonic energy loss is seen in central PbPb collisions at the LHC.
A new scenario, alternative to energy loss, for the observed suppression of high-pT hadrons observed at RHIC is proposed. In the limit of a very dense medium crated in nuclear collisions the mean free-path of the produced (pre)hadron vanishes, and and the nuclear suppression, R_{AA} is completely controlled by the production length. The RHIC data are well explained in a parameter free way, and predictions for LHC are provided.
Since large $p_T$ particles in high-energy hadronic or nuclear collisions come from jet fragmentation, jet quenching due to parton energy loss in dense matter will cause the suppression of large $p_T$ hadron spectra in high-energy heavy-ion collisions. Assuming an effective energy loss $dE/dx$ for the high $E_T$ partons, effective jet fragmentation functions are constructed in which leading hadrons will be suppressed. Using such effective fragmentation functions, high $p_T$ hadron spectra and particle suppression factors relative to $pp$ collisions are estimated in central high-energy nuclear …
We present results for the quenching, elliptic flow and azimuthal correlations of heavy flavour particles in high-energy nucleus-nucleus collisions obtained through the POWLANG transport setup, developed in the past to study the propagation of heavy quarks in the Quark-Gluon Plasma and here extended to include a modeling of their hadronization in the presence of a medium. Hadronization is described as occurring via the fragmentation of strings with endpoints given by the heavy (anti-)quark Q(Qbar) and a thermal parton qbar(q) from the medium. The flow of the light quarks is shown to affect sig…
I examine the role of final state interactions in cold nuclear matter in modifying hadron production on nuclear targets with leptonic or hadronic beams. I demonstrate the extent to which available experimental data in electron-nucleus collisions can give direct information on final state effects in hadron-nucleus and nucleus-nucleus collisions. For hadron-nucleus collisions, a theoretical estimate based on a parton energy loss model tested in lepton-nucleus collisions shows a large effect on mid-rapidity hadrons at fixed target experiments. At RHIC energy, the effect is large for negative rapi…
Recently we have conjectured that (in-)elastic collisions of (pre-)hadronic high momentum states with the bulk of hadrons in the late fireball might substantially account for the attenuation of the high transverse momentum hadrons at RHIC. The potential hadronic attenuation has therefore to be addressed in further detail before definite conclusions on possible QCD effects in a deconfined QGP phase can be drawn with respect to the materializing jets. From our transport studies we find that the interactions of fully formed hadrons are practically negligible in central Au+Au collisions at \sqrt s…
In nucleus-nucleus collisions at the Relativistic Heavy Ion Collider (RHIC), one generically observes a strong medium-induced suppression of high-pT hadron production. This suppression is accounted for in models which assume a significant medium-induced radiative energy loss of high-pT parent partons produced in the collision. How can we further test the microscopic dynamics conjectured to underly this abundant high-pT phenomenon? What can we learn about the dynamics of parton fragmentation, and what can we learn about the properties of the medium which modifies it ? Given that inelastic parto…
Parton propagation in dense nuclear matter results in elastic, inelastic and coherent multiple soft scattering with the in-medium color charges. Such scattering leads to calculable modifications of the hadron production cross section that is evaluated in the framework of the perturbative QCD factorization approach. Final state medium-induced gluon bremsstrahlung is arguably the most efficient way of suppressing large transverse momentum particle production in nucleus-nucleus collisions. The observed hadronic attenuation, known as jet quenching, can be related to the properties of the medium, s…
The generic features of parton energy loss effects on the quenching of single hadron spectra in heavy-ion collisions are discussed, paying attention to the expected differences from RHIC to LHC. The need for precise baseline measurements in p-Pb collisions at the LHC is also emphasized. Finally I briefly mention the production of prompt photons in heavy-ion collisions as well as some open questions.
The suppression of high momentum particles in heavy-ion collisions in comparison to elementary reactions is one of the main indications for the formation of a quark-gluon plasma. In recent studies, full jets are being reconstructed and substructure observables are gaining importance in assessing the medium modifications of hard probes. In this work, the effect of the late stage hadronic interactions are explored within the hadronic transport approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). High momentum particles are incorporated in a radially expanding hadron gas to …
We study within the light-cone path integral approach [3] the effect of the induced gluon radiation on high-p_{T} hadrons in high-energy heavy-ion collisions. The induced gluon spectrum is represented in a new form which is convenient for numerical simulations. For the first time, computations are performed with a realistic parametrization of the dipole cross section. The results are in reasonable agreement with suppression of high-p_{T} hadrons in Au+Au collisions at \sqrt{s}=200 GeV observed at RHIC.
A new shooting string holographic model of jet quenching of light quarks in strongly coupled plasmas is presented to overcome the phenomenological incompatibilities of previous falling string holographic scenarios that emerged when confronted with the recent LHC data. This model is based on strings with finite momentum endpoints that start close to the horizon and lose energy as they approach the boundary. This framework is applied to compute the nuclear modification factor RAA of light hadrons at RHIC and LHC, showing that this model improves greatly the comparison with the recent light hadro…
The sensitivity of semi-hard (p_\perp < 10 GeV) hadron production to parton energy loss in high energy nuclear collisions is studied via the HIJING1.35 model. We test the model on recent WA98 data on 160 AGeV Pb+Pb -> pi^0 up to 4 GeV/c and while these data are reproduced, the results depends sensitively on the model of the Cronin effect. At (RHIC) collider energies (s^1/2 > 200 AGeV), on the other hand, semi-hard hadron production becomes insensitive to the above model and is thus expected to be a cleaner probe of jet quenching signature associated with non-Abelian radiative energy loss.
The $p_\perp$ dependence of the nuclear modification factor $R_{\rm AA}$ measured in PbPb collisions at the LHC exhibits a universal shape, which can be very well reproduced in a simple energy loss model based on the BDMPS medium-induced gluon spectrum. The scaling is observed for various hadron species ($h^\pm$, $D$, $J/ψ$) in different centrality classes and at both colliding energies, $\sqrt{s}=2.76$ TeV and $\sqrt{s}=5.02$ TeV. Results indicate an 10-20% increase of the transport coefficient from $\sqrt{s}=2.76$ TeV to $\sqrt{s}=5.02$ TeV, consistent with that of particle multiplicity. Bas…
Hydrodynamics and jet quenching are responsible for the elliptic flow $v_2$ and suppression of large transverse momentum ($p_T$) hadrons, respectively, two of the most important phenomena leading to the discovery of a strongly coupled quark-gluon plasma (QGP) in high-energy heavy-ion collisions. A consistent description of the hadron suppression factor $R_{AA}$ and $v_2$, especially at intermediate $p_T$, however, remains a challenge. We solve this long-standing $R_{AA}\otimes v_2$ puzzle by including quark coalescence for hadronization and final state hadron cascade in the coupled linear Bolt…
We present an updated analysis of the coherent neutrino-nucleus elastic scattering data of the COHERENT experiment taking into account the new quenching factor published recently in Phys. Rev. D100, 033003 (2019). Through a fit of the COHERENT time-integrated energy spectrum, we show that the new quenching factor leads to a better determination of the average rms radius of the neutron distributions of $^{133}\text{Cs}$ and $^{127}\text{I}$, while in combination with the atomic parity violation (APV) experimental results it allows to determine a data-driven APV measurement of the low-energy wea…
Data on low-pT hadronic spectra are widely regarded as evidence of a hydrodynamic expansion in nucleus-nucleus collisions. In this interpretation, different hadron species emerge from a common medium that has built up a strong collective velocity field. Here, we show that the existence of a collective flow field implies characteristic modifications of high-pT parton fragmentation. We generalize the formalism of parton energy loss to the case of flow-induced, oriented momentum transfer. We also discuss how to embed this calculation in hydrodynamic simulations. Flow effects are found to result g…
In most calculations of hard particle suppression in heavy-ion reactions the hadronic stage has been neglected due to formation time arguments. Most of the hard particle shower exits the hot and dense medium before the system enters the hadronic evolution. In this contribution, a first assessment within the hadronic transport approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) of rescattering effects on hard particles is presented. In particular, it is shown that the hadronic energy loss depends on the particle species as well as the energy of the probe. A parametrization…
Recent measurements of the germanium quenching factor deviate significantly from the predictions of the standard Lindhard model for nuclear recoil energies below a keV. This departure may be explained by the Migdal effect in neutron scattering on germanium. We show that the Migdal effect on the quenching factor can mimic the signal of a light Z' or light scalar mediator in coherent elastic neutrino nucleus scattering experiments with reactor antineutrinos. It is imperative that the quenching factor of nuclei with low recoil energy thresholds be precisely measured close to threshold to avoid su…
The suppression of high transverse momentum (P_T) jets and hadrons in ultrarelativistic heavy-ion collisions with respect to a p-p baseline in terms of the nuclear suppression factor R_AA is one of the key observables to gauge the density of a hot and dense QCD medium. However, the suppression measured by R_AA is not a straightforward measure of the medium properties, the value of the observable also depends on the ratio of quark to gluon jets and on the slope of the hard parton spectrum, which explains why R_AA is found to be fairly similar at RHIC and LHC despite the very different dynamics.…
We discuss the potential information about highly excited QCD-matter provided by medium-induced partonic energy loss, known as ``jet quenching''. In particular, with its large acceptance hadronic and electromagnetic calorimetry, the Compact Muon Solenoid detector at LHC collider is a promising device to study these effects. We present physics simulations of observables such as the jet distribution with impact parameter, the azimuthal anisotropy of jet quenching, and the effects of b-quark energy loss on the high-mass dimuon continuum and secondary charmonium production.
A parton produced with a high transverse momentum in a hard collision is regenerating its color field, intensively radiating gluons and losing energy. This process cannot last long, if it ends up with production of a leading hadron carrying the main fraction z_h of the initial parton momentum. So energy conservation imposes severe constraints on the length scale of production of a single hadron with high pT. As a result, the main reason for hadron quenching observed in heavy ion collisions, is not energy loss, but attenuation of the produced colorless dipole in the created dense medium. The la…
A recent new measurement and re-analysis of past measurements suggested an improved quenching factor value and uncertainty for CsI[Na]. This implies a measurement of the COHERENT experiment of coherent elastic neutrino-nucleus scattering that is closer to the Standard Model prediction and has less uncertainty. We illustrate the impact of this improvement by revisiting fits to the Weinberg angle, neutrino magnetic moments, neutron rms and neutrino charge radii, neutrino non-standard interactions (in particular those relevant for LMA-Dark) and new scalar as well as vector bosons. Significant imp…
The value of the parton to hadron fragmentation function in QCD in vacuum (for example from proton-proton collisions at high energy colliders) is directly/indirectly used in the literature to study the jet quenching and the hadron production from quark-gluon plasma at RHIC and LHC. In this paper we show that this is not possible because, unlike the perturbative propagator in non-equilibrium QCD, the parton to hadron fragmentation function is a non-perturbative quantity in QCD and hence it is not possible to decompose the fragmentation function in non-equilibrium QCD into the vacuum part and th…
The flow pattern and evolution of the medium created in ultrarelativistic heavy ion collisions can have significant influence on the energy loss of hard partons traversing the medium. We demonstrate that within a range of assumptions for longitudinal and transverse flow which are all compatible with the measured hadronic single particle distributions, the quenching power of the medium can vary within almost a factor five. Thus, the choice of the medium evolution is one of the biggest uncertainties in jet quenching calculations and needs to be addressed with some care.
The suppression of hadron p_T spectra in high energy central heavy-ion collisions compared to proton-proton collisions, referred to as 'jet-quenching', is currently attributed to partonic energy loss in the hot medium created in the collision. The RHIC experiments show that at large enough p_T, hadron quenching is strong, and of similar magnitude for light and heavy flavours. This point is difficult to understand in a parton energy loss scenario, where the energy loss is believed to be dominantly radiative, and quantitatively different for light partons and heavy quarks: gluon radiation off a …
Fully dynamic simulations of heavy ion collisions at RHIC and at LHC energies within the perturbative QCD-based partonic transport model BAMPS (Boltzmann Approach to Multi-Parton Scatterings) are presented, focusing on the simultaneous investigation of jet quenching and elliptic flow. The model features inelastic 2 <-> 3 processes based on the Gunion-Bertsch matrix element and has recently been extended to include light quark degrees of freedom, allowing for direct comparison to hadronic data on the nuclear modification factor via a fragmentation scheme for high-pT partons. The nuclear modific…
We report the evolution effects on jet energy loss with detailed balance. The initial conditions and parton evolution based on perturbative QCD in the chemical non-equilibrated medium and Bjorken expanding medium at RHIC are determined. The parton evolution affect the jet energy loss evidently. This will increase the energy and propagating distance dependence of the parton energy loss and will affect the shape of suppression of moderately high P_{T} hadron spectra.
We study the dependence of parton energy loss (quenching) on rapidity in ultra-relativistic nuclear collisions at RHIC. This can provides invaluable information on the density of the medium, which should be more dilute going away from mid-rapidity, thereby reducing the effect of quenching. We predict a clear effect at moderate transverse momenta $\sim$ 3 GeV.
In the framework of soft-collinear effective theory with Glauber gluons, results and predictions for inclusive hadron suppression, based upon in-medium parton shower evolution, are presented for Au+Au and Pb+Pb collisions at RHIC and LHC energies $\sqrt{s}=200$ AGeV and $\sqrt{s}=2.76, \, 5.1$ ATeV, respectively. The $\rm SCET_G$ medium-induced splitting kernels are further implemented to evaluate the attenuation of reconstructed jet cross in such reactions and to examine their centrality and radius $R$ dependence. Building upon a previously developed method to systematically resum the jet sha…
The $p_\perp$ dependence of the nuclear modification factor $R_{\text{AA}}$ measured in PbPb collisions at the LHC exhibits a universal shape, which can be very well reproduced in a simple energy loss model based on the BDMPS medium-induced gluon spectrum. We update a former study by including in the analysis the recent CMS measurements on $J/ψ$ production in PbPb collisions at $\sqrt{s}=5.02$ TeV and charged hadron production in XeXe collisions at $\sqrt{s}=5.44$ TeV. The average parton energy loss extracted from minimum bias XeXe collisions is reduced typically by 20% compared to PbPb collis…
In the framework of the HIJING model global characteristics of nucleus- nucleus collisions are studied for a Large Hadron Collider energy scale. An interesting model prediction is the presence of a central bump over a pseudorapidity plateau of a total transverse energy distribution. The bump is induced by a jet quenching effect in a dense nuclear matter. It is shown that on a wide acceptance calorimeter with a pseudorapidity coverage -5 < η< 5 allow to obtain experimental confirmation of such an effect.
Multiple interactions between parton showers and the surrounding QCD matter are expected to underlie the strong medium-modifications of jet observables in ultra-relativistic heavy ion collisions at RHIC and at the LHC. Here, we note that such jet-medium interactions alter generically and characteristically the color correlations in the parton shower. We characterize these effects in a color-differential calculation of the medium-induced gluon radiation spectrum to first and second order in opacity. By interfacing simple branching histories of medium-modified color flow with the Lund hadronizat…
We study jet quenching in $pp$ and $pA$ collisions in the scenario with formation of a mini quark-gluon plasma. We find a significant suppression effect. For light hadrons at $p_{T}\sim 10$ GeV we obtained the reduction of the spectra by $\sim [20-30,25-35,30-40]$\% in $pp$ collisions at $\sqrt{s}=[0.2, 2.76,7]$ TeV. We discuss how jet quenching in $pp$ collisions may change the predictions for the nuclear modification factors in $AA$ collisions for light and heavy flavors. We also give predictions for modification of the photon-tagged and inclusive jet fragmentation functions in high multipli…
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…
We evaluate the medium suppression of light hadron spectra in $pp$ collisions at RHIC and LHC energies in the scenario with formation of a mini quark-gluon plasma. We find a significant suppression effect. For $p_{T}\sim 10$ GeV we obtained the reduction of the spectra by $\sim [20-30,25-35,30-40]$ % at $\sqrt{s}=[0.2, 2.76,7]$ TeV. We also discuss how this phenomenon may change the predictions for the nuclear modification factors for $AA$ and $pA$ collisions.
The photoproduction of quarkonium in coherent hadron-hadron (pp/pA/AA$) interactions for LHC energies is an important tool to investigate the QCD dynamics at high energies. In this paper we estimate the integrated cross section and rapidity distribution for J/Psi and Upsilon production using the Color Glass Condensate (CGC) formalism. We predict large rates, implying that the experimental identification could be feasible at the LHC.
Jets produced in nucleus-nucleus collisions at the LHC are expected to be strongly modified due to the interaction of the parton shower with the dense QCD matter. Here, we point out that jet quenching can leave signatures not only in the longitudinal and transverse jet energy and multiplicity distributions, but also in the hadrochemical composition of the jet fragments. In particular, we show that even in the absence of medium effects at or after hadronization, the medium-modification of the parton shower can result in significant changes in jet hadrochemistry. We discuss how jet hadrochemistr…
The energy loss of a hard parton is regarded as a useful tool to probe properties of a soft medium. However, the information obtained by a measurement of the nuclear suppression R_AA is not very sensitive to medium properties. Thus, more differential observables are needed. Here we focus on the pattern of angular correlation of hadrons associated with a hard trigger. These show rich pattern when going from low p_T to high p_T associate momentum. At low p_T, the pattern of associate hadrons can be understood in terms of Mach shocks excited by the energy lost from the away side parton while the …
