A. Majumder

Wayne State University, Detroit, Michigan, United States

Are you A. Majumder?

Claim your profile

Publications (72)224.71 Total impact

  • Guang-You Qin, Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: We study the effect of multiple scatterings on the propagation of hard partons and the production of jet-bremsstrahlung photons inside a dense medium in the framework of deep-inelastic scattering off a large nucleus. We include the momentum exchanges in both longitudinal and transverse directions between the hard partons and the constituents of the medium. Keeping up to the second order in a momentum gradient expansion, we derive the spectrum for the photon emission from a hard quark jet when traversing dense nuclear matter. Our calculation demonstrates that the photon bremsstrahlung process is influenced not only by the transverse momentum diffusion of the propagating hard parton, but also by the longitudinal drag and diffusion of the parton momentum. A notable outcome is that the longitudinal drag tends to reduce the amount of stimulated emission from the hard parton.
    11/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Within five different approaches to parton propagation and energy loss in dense matter, a phenomenological study of experimental data on suppression of large $p_T$ single inclusive hadrons in heavy-ion collisions at both RHIC and LHC was carried out. The evolution of bulk medium used in the study for parton propagation was given by 2+1D or 3+1D hydrodynamic models which are also constrained by experimental data on bulk hadron spectra. Values for the jet transport parameter $\hat q$ at the center of the most central heavy-ion collisions are extracted or calculated within each model, with parameters for the medium properties that are constrained by experimental data on the hadron suppression factor $R_{AA}$. For a quark with initial energy of 10 GeV we find that $\hat q\approx 1.1 \pm 0.3$ GeV$^2$/fm at an initial time $\tau_0=0.6$ fm/$c$ in Au+Au collisions at $\sqrt{s}=200$ GeV/n and $\hat q\approx 1.9 \pm 0.7 $ GeV$^2$/fm in Pb+Pb collisions at $\sqrt{s}=2.76 $ TeV/n. Compared to earlier studies, these represent significant convergence on values of the extracted jet transport parameter, reflecting recent advances in theory and the availability of new experiment data from the LHC.
    12/2013;
  • Source
    Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: The propagation of a virtual quark in a thermal medium is considered. The non-perturbative jet transport coefficient $\hat{q}$ is estimated in quark less SU(2) lattice gauge theory. The light like correlator which defines $\hat{q}$, defined in the regime where the jet has small virtuality compared to its energy, is analytically related to a series of local operators in the deep Euclidean region, where the jet's virtuality is of the same order as its energy. It is demonstrated that in this region, for temperatures in the range of T=400-600 MeV, and for jet energies above 20 GeV, the leading term in the series is dominant over the next-to-leading term and thus yields an estimate of the value of $\hat{q}$. In these proceedings we discuss the details of the numerical calculation.
    Nuclear Physics A 03/2013; · 2.50 Impact Factor
  • Source
    Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: We outline a novel approach to develop an in-medium shower Monte-Carlo event generator based on the higher-twist formalism of jet modification. By undoing one of the light-cone integrals which sets the corresponding light-cone momentum to be equal in the amplitude and the complex conjugate, we introduce an uncertainty in the smaller light-cone momentum component. This allows for the generalization of the standard analytic formalism to a Wigner transform like formalism, where the non-conjugate large light-cone momentum and position are retained for each parton. Jets are generated event-by-event by simulating this Wigner transform kernel. Simple results for longitudinal distributions of partons and hadrons from jets propagating through a hot brick of strongly interacting matter are presented. Values of the transport coefficient $\hat{q}$ are dialed to match phenomenologically relevant cases.
    Physical Review C 01/2013; 88(1). · 3.72 Impact Factor
  • Source
    A Majumder, C Shen
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a parameter-free postdiction of the high-p_{T} charged-hadron nuclear modification factor (R_{AA}) in two centralities, measured by the CMS Collaboration in Pb-Pb collisions at the LHC. The evolution of the bulk medium is modeled using viscous fluid dynamics, with parameters adjusted to describe the soft hadron yields and elliptic flow. Assuming the dominance of radiative energy loss, we compute the medium modification of the R_{AA} using a perturbative QCD-based formalism, the higher twist scheme. The transverse momentum diffusion coefficient q[over ^] is assumed to scale with the entropy density and is normalized by fitting the R_{AA} in the most central Au-Au collisions at the Relativistic Heavy-Ion Collider. This setup is validated in noncentral Au-Au collisions at the Relativistic Heavy-Ion Collider and then extrapolated to Pb-Pb collisions at the LHC, keeping the relation between q[over ^] and entropy density unchanged. We obtain a satisfactory description of the CMS R_{AA} over the p_{T} range from 10 to 100 GeV.
    Physical Review Letters 11/2012; 109(20):202301. · 7.73 Impact Factor
  • A. Majumder, C. Shen
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a parameter-free postdiction of the high-pT charged-hadron nuclear modification factor (RAA) in two centralities, measured by the CMS Collaboration in Pb-Pb collisions at the LHC. The evolution of the bulk medium is modeled using viscous fluid dynamics, with parameters adjusted to describe the soft hadron yields and elliptic flow. Assuming the dominance of radiative energy loss, we compute the medium modification of the RAA using a perturbative QCD-based formalism, the higher twist scheme. The transverse momentum diffusion coefficient q̂ is assumed to scale with the entropy density and is normalized by fitting the RAA in the most central Au-Au collisions at the Relativistic Heavy-Ion Collider. This setup is validated in noncentral Au-Au collisions at the Relativistic Heavy-Ion Collider and then extrapolated to Pb-Pb collisions at the LHC, keeping the relation between q̂ and entropy density unchanged. We obtain a satisfactory description of the CMS RAA over the pT range from 10 to 100 GeV.
    Physical Review Letters 11/2012; 109(20). · 7.73 Impact Factor
  • Source
    Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: The formalism of jet modification in the higher twist approach is modified to describe a hard parton propagating through a hot thermalized medium. The leading order contribution to the transverse momentum broadening of a high energy (near on-shell) quark in a thermal medium is calculated. This involves a factorization of the perturbative process of scattering of the quark from the non-perturbative transport coefficient. An operator product expansion of the non-perturbative operator product which represents $\hat{q}$ is carried out and related via dispersion relations to the expectation of local operators. These local operators are then evaluated in quenched SU(2) lattice gauge theory.
    Nuclear Physics A 10/2012; · 2.50 Impact Factor
  • Source
    Guang-You Qin, Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: The effect of multiple scatterings on the propagation of hard partonic jets in a dense nuclear medium is studied in the framework of deep-inelastic scattering (DIS) off a large nucleus. Power counting arguments based on the Glauber improved Soft-Collinear-Effective-Theory are used to identify the class of leading power corrections to the process of a single parton traversing the extended medium without emission. It turns out that the effect of longitudinal drag and diffusion (often referred to as straggling) is as important as transverse scattering, when relying solely on power counting arguments. With the inclusion of momentum exchanges in both transverse and longitudinal directions between the traversing hard parton and the constituents of the medium, we derive a differential equation for the time (or distance) evolution of the hard parton momentum distribution. Keeping up to the second order in a momentum gradient expansion, this equation describes in-medium evolution of hard jets which experience longitudinal drag and diffusion plus the transverse broadening caused by multiple scatterings from the medium.
    Physical Review C 05/2012; 87(2). · 3.72 Impact Factor
  • Source
    Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a framework where first principles calculations of jet modification may be carried out in a non-perturbative thermal environment. As an example of this approach, we compute the leading order contribution to the transverse momentum broadening of a high energy (near on-shell) quark in a thermal medium. This involves a factorization of a non-perturbative operator product from the perturbative process of scattering of the quark. An operator product expansion of the non-perturbative operator product is carried out and related via dispersion relations to the expectation of local operators. These local operators are then evaluated in quenched SU(2) lattice gauge theory.
    Physical Review C 02/2012; 87(3). · 3.72 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We review the currently available formalisms for radiative energy loss of a high-momentum parton in a dense strongly interacting medium. The underlying theoretical framework of the four commonly used formalisms is discussed and the differences and commonalities between the formalisms are highlighted. A quantitative comparison of the single gluon emission spectra as well as the energy loss distributions is given for a model system consisting of a uniform medium with a fixed length of L=2 fm and L=5 fm (the `Brick'). Sizable quantitative differences are found. The largest differences can be attributed to specific approximations that are made in the calculation of the radiation spectrum.
    Physical Review C 06/2011; 86(6). · 3.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We review the currently available formalisms for radiative energy loss of a high-momentum parton in a dense strongly interacting medium. The underlying theoretical framework of the four commonly used formalisms is discussed and the differences and commonalities between the formalisms are highlighted. A quantitative comparison of the single gluon emission spectra as well as the energy loss distributions is given for a model system consisting of a uniform medium with a fixed length of L=2 fm and L=5 fm (the `Brick'). Sizable quantitative differences are found. The largest differences can be attributed to specific approximations that are made in the calculation of the radiation spectrum.
    01/2011;
  • Source
    Abhijit Majumder, Berndt Müller
    [Show abstract] [Hide abstract]
    ABSTRACT: Finite temperature lattice simulations of quantum chromodynamics (QCD) are sensitive to the hadronic mass spectrum for temperatures below the "critical" temperature T(c) ≈ 160 MeV. We show that a recent precision determination of the QCD trace anomaly shows evidence for the existence of a large number of hadron states beyond those known from experiment. The lattice results are well represented by an exponentially growing mass spectrum up to a temperature T=155 MeV. Using simple parametrizations of the hadron mass spectrum we show how one may estimate the total spectral weight in these yet undermined states.
    Physical Review Letters 12/2010; 105(25):252002. · 7.73 Impact Factor
  • Source
    Guang-You Qin, Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a successful description of the medium modification of light and heavy flavor jets within a perturbative-QCD-based approach. Only the couplings involving hard partons are assumed to be weak. The effect of the medium on a hard parton, per unit time, is encoded in terms of three nonperturbative, related transport coefficients which describe the transverse momentum squared gained, the elastic energy loss, and diffusion in elastic energy transfer. Scaling the transport coefficients with the temperature of the medium, we achieve a good description of the centrality dependence of the suppression and the azimuthal anisotropy of leading hadrons. Imposing additional constraints based on leading order (LO) hard thermal loop (HTL) effective theory leads to a worsening of the fit, implying the necessity of computing transport coefficients beyond LO HTL.
    Physical Review Letters 12/2010; 105(26):262301. · 7.73 Impact Factor
  • Source
    Masayuki Asakawa, Abhijit Majumder, Berndt Müller
    [Show abstract] [Hide abstract]
    ABSTRACT: We discuss various mechanisms for the creation of an asymmetric charge fluctuation with respect to the reaction plane among hadrons emitted in relativistic heavy-ion collisions. We show that such mechanisms exist in both, the hadronic gas and the partonic phases of QCD. The mechanisms considered here all require the presence of a strong magnetic field (the ``chiral magnetic effect''), but they do not involve parity or charge-parity violations. We analyze how a transient local electric current fluctuation generated by the chiral magnetic effect can dynamically evolve into an asymmetric charge distribution among the final-state hadrons in momentum space. We estimate the magnitude of the event-by-event fluctuations of the final-state charge asymmetry due to the partonic and hadronic mechanisms.
    Physical Review C 03/2010; · 3.72 Impact Factor
  • Source
    A. Majumder, M. Van Leeuwen
    [Show abstract] [Hide abstract]
    ABSTRACT: The study of the structure of strongly interacting dense matter via hard jets is reviewed. High momentum partons produced in hard collisions produce a shower of gluons prior to undergoing the non-perturbative process of hadronization. In the presence of a dense medium this shower is modified due to scattering of the various partons off the constituents in the medium. The modified pattern of the final detected hadrons is then a probe of the structure of the medium as perceived by the jet. Starting from the factorization paradigm developed for the case of particle collisions, we review the basic underlying theory of medium induced gluon radiation based on perturbative Quantum Chromo Dynamics (pQCD) and current experimental results from Deep Inelastic Scattering on large nuclei and high energy heavy-ion collisions, emphasizing how these results constrain our understanding of energy loss. This review contains introductions to the theory of radiative energy loss, elastic energy loss, and the corresponding experimental observables and issues. We close with a discussion of important calculations and measurements that need to be carried out to complete the description of jet modification at high energies at future high energy colliders.
    Progress in Particle and Nuclear Physics 02/2010; 66. · 2.26 Impact Factor
  • Berndt Mueller, Masayuki Asakawa, Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: We discuss several mechanisms for the creation of a charge asymmetry with respect to the reaction plane among hadrons emitted in relativistic heavy-ion collisions. We show that such mechanisms exist in both, the hadron gas and the quark-gluon plasma phase. All such mechanisms have in common that they require the presence of a strong magnetic field (the ``chiral magnetic effect''), but they do not involve P or PC symmetry violations. We analyze how a transient local electric current generated by the chiral magnetic effect can dynamically evolve into a charge asymmetry of the final-state hadron distribution in momentum space. We estimate the magnitude of the event-by-event fluctuations of the final-state charge asymmetry due to the partonic and hadronic mechanisms. )
    02/2010;
  • Source
    Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: The energy loss of hard jets produced in the Deep-Inelastic scattering (DIS) off a large nucleus is considered in the collinear limit. In particular, the single gluon emission cross section due to multiple scattering in the medium is calculated. Calculations are carried out in the higher-twist scheme, which is extended to include contributions from multiple transverse scatterings on both the produced quark and the radiated gluon. The leading length enhanced parts of these power suppressed contributions are resummed. Various interferences between such diagrams lead to the Landau-Pomeranchuk-Migdal (LPM) effect. We resum the corrections from an arbitrary number of scatterings and isolate the leading contributions which are suppressed by one extra power of the hard scale $Q^{2}$. All powers of the emitted gluon forward momentum fraction $y$ are retained. We compare our results with the previous calculation of single scattering per emission in the higher-twist scheme as well as with multiple scattering resummations in other schemes. It is found that the leading ($1/Q^2$) contribution to the double differential gluon production cross section, in this approach, is equivalent to that obtained from the single scattering calculation once the transverse momentum of the final quark is integrated out. We comment on the generalization of this formalism to Monte-Carlo routines.
    Physical review D: Particles and fields 12/2009;
  • Source
    Guang-You Qin, Abhijit Majumder
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a successful description of the medium modification of light and heavy flavor jets within a perturbative QCD (pQCD) based approach. Only the couplings involving hard partons are assumed to be weak. The effect of the medium on a hard parton, per unit time, is encoded in terms of three non-perturbative, related transport coefficients which describe the transverse momentum squared gained, the elastic energy loss and diffusion in elastic energy transfer. A fit of the centrality dependence of the suppression and the azimuthal anisotropy of leading hadrons tends to favor somewhat larger transport coefficients for heavy quarks. Imposing additional constraints based on leading order (LO) Hard Thermal Loop (HTL) effective theory, leads to a worsening of the fit. Comment: v2, 4 pages, 3 figures
    10/2009;
  • Source
    G-Y Qin, A Majumder, H Song, U Heinz
    [Show abstract] [Hide abstract]
    ABSTRACT: For a hard parton moving through a dense QCD medium, we compute self-consistently the energy loss and the fraction deposited into the medium due to showering and rescattering of the shower, assuming weak coupling between probe and medium. The same transport coefficients thus determine both the energy loss and its deposition into the medium. This allows a parameter free calculation of the latter once the former are computed or measured. We compute them for a weakly interacting medium. Assuming a short thermalization time for the deposited energy, we determine the medium's hydrodynamical response and obtain a conical pattern that is strongly enhanced by showering.
    Physical Review Letters 10/2009; 103(15):152303. · 7.73 Impact Factor
  • Source
    A. Majumder, B. Müller, St. Mrowczynski
    [Show abstract] [Hide abstract]
    ABSTRACT: The average transverse momentum transfer per unit path length to a fast parton scattering elastically in a perturbative quark-gluon plasma is related to the radiative energy loss of the parton. We first calculate the momentum transfer coefficient $\hat q$ in terms of a classical Langevin problem and then define it quantum-mechanically through scattering matrix element. After treating the well known case of a quark-gluon plasma in equilibrium we consider an off-equilibrium unstable plasma. As a specific example, we treat the two-stream plasma with unstable modes of longitudinal chromoelectric field. In the presence of the instabilities, $\hat q$ is shown to exponentially grow in time. Comment: Updated version containing an analysis of insufficiencies in previous calculations of momentum broadening in unstable plasmas
    Physical review D: Particles and fields 03/2009;

Publication Stats

1k Citations
224.71 Total Impact Points

Institutions

  • 2012
    • Wayne State University
      Detroit, Michigan, United States
  • 2010–2012
    • The Ohio State University
      • Department of Physics
      Columbus, Ohio, United States
  • 2006–2010
    • Duke University
      • Department of Physics
      Durham, NC, United States
  • 2003–2006
    • Lawrence Berkeley National Laboratory
      • Nuclear Science Division
      Berkeley, CA, United States
  • 1999–2002
    • McGill University
      • Department of Physics
      Montréal, Quebec, Canada