# W. A. Horowitz

## Contact Details

NameW. A. Horowitz |
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## Pub CategoriesNuclear Theory (32) High Energy Physics - Phenomenology (30) High Energy Physics - Theory (6) Nuclear Experiment (5) High Energy Physics - Experiment (2) High Energy Physics - Lattice (1) |

## Publications Authored By W. A. Horowitz

We use an energy loss model sensitive to thermal fluctuations to compute the azimuthal and momentum correlations of $b\bar{b}$ pairs traversing a strongly coupled plasma from Pb+Pb collisions at LHC ($\sqrt{s}=2.76\text{TeV}$). The azimuthal correlations are compared with those from perturbative QCD based simulations. Read More

We show for the first time in over 50 years how to correctly apply the Kinoshita-Lee-Nauenberg theorem diagrammatically in a next-to-leading order scattering process. We improve on previous works by including all initial and final state soft radiative processes, including absorption and an infinite sum of partially disconnected amplitudes. Crucially, we exploit the Monotone Convergence Theorem to prove that our delicate rearrangement of this formally divergent series is correct. Read More

**Authors:**G. Aarts, J. Aichelin, C. Allton, R. Arnaldi, S. A. Bass, C. Bedda, N. Brambilla, E. Bratkovskaya, P. Braun-Munzinger, G. E. Bruno, T. Dahms, S. K. Das, H. Dembinski, M. Djordjevic, E. G. Ferreiro, A. Frawley, P. -B. Gossiaux, R. Granier de Cassagnac, A. Grelli, M. He, W. Horowitz, G. M. Innocenti, M. Jo, O. Kaczmarek, P. G. Kuijer, M. Laine, M. P. Lombardo, A. Mischke, M. Munhoz, M. Nahrgang, M. Nguyen, A. C. Oliveira da Silva, P. Petreczky, A. Rothkopf, M. Schmelling, E. Scomparin, T. Song, J. Stachel, A. Suaide, L. Tolos, B. Trzeciak, A. Uras, L. van Doremalen, L. Vermunt, S. Vigolo, N. Xu, Z. Ye, H. Zanoli, P. Zhuang

Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop "Tomography of the quark-gluon plasma with heavy quarks}, which was held in October 2016 in Leiden, the Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma. Read More

We present the first ever AdS/CFT calculation of $\hat{q}$ for a light quark jet as a function of position or, equivalently, time. Our result does not suffer from the gamma factor blow up of the usual time-independent AdS/CFT heavy quark setup and is qualitatively similar to, but differs by $\sim\mathcal{O}(1)$ factor from, the light flavor result of Liu, Rajagopal, and Wiedemann. Our findings can be immediately implemented into any $\hat{q}$-based energy loss model. Read More

We compute the average squared distance, $s^2(t)$, travelled by a light-flavour off-mass-shell coloured parton in a strongly-coupled $\mathcal{N}=4$ $SU(N_c)$ super-symmetric Yang Mills plasma using the gauge/string duality. In fact, we derive a closed integral expression for $s^2(t;a)$ in $AdS_3$-Schwarzschild, which interpolates between a heavy quark when $a = 0$ and a light quark when $a = 1$, that we evaluate analytically for small virtualities - labelled $s_\text{small}^2(t;a)$. For arbitrary virtualities, we show that for asymptotically early times the motion is ballistic, $\left. Read More

We use perturbative quantum chromodynamics to compute the corrections to the energy loss of a hard particle due to short separation distances between the creation of the particle and the in-medium scattering center that stimulates bremsstrahlung radiation. The result has several surprising features. The correction 1) does not go to zero for large path lengths; 2) breaks color triviality; 3) is formally zero in the large formation time approximation, but numerically dominates at large ~100 GeV parent parton energies out to long ~3 fm paths. Read More

Recent surprising discoveries of collective behaviour of low-$p_T$ particles in $pA$ collisions at LHC hint at the creation of a hot, fluid-like QGP medium. The seemingly conflicting measurements of non-zero particle correlations and $R_{pA}$ that appears to be consistent with unity demand a more careful analysis of the mechanisms at work in such ostensibly minuscule systems. We study the way in which energy is dissipated in the QGP created in $pA$ collisions by calculating, in pQCD, the short separation distance corrections to the well-known DGLV energy loss formulae that have produced excellent predictions for $AA$ collisions. Read More

**Authors:**A. Andronic, F. Arleo, R. Arnaldi, A. Beraudo, E. Bruna, D. Caffarri, Z. Conesa del Valle, J. G. Contreras, T. Dahms, A. Dainese, M. Djordjevic, E. G. Ferreiro, H. Fujii, P. B. Gossiaux, R. Granier de Cassagnac, C. Hadjidakis, M. He, H. van Hees, W. A. Horowitz, R. Kolevatov, B. Z. Kopeliovich, J. P. Lansberg, M. P. Lombardo, C. Lourenco, G. Martinez-Garcia, L. Massacrier, C. Mironov, A. Mischke, M. Nahrgang, M. Nguyen, J. Nystrand, S. Peigne, S. Porteboeuf-Houssais, I. K. Potashnikova, A. Rakotozafindrabe, R. Rapp, P. Robbe, M. Rosati, P. Rosnet, H. Satz, R. Schicker, I. Schienbein, I. Schmidt, E. Scomparin, R. Sharma, J. Stachel, D. Stocco, M. Strickland, R. Tieulent, B. A. Trzeciak, J. Uphoff, I. Vitev, R. Vogt, K. Watanabe, H. Woehri, P. Zhuang

This report reviews the study of open heavy-flavour and quarkonium production in high-energy hadronic collisions, as tools to investigate fundamental aspects of Quantum Chromodynamics, from the proton and nucleus structure at high energy to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is given to the lessons learnt from LHC Run 1 results, which are reviewed in a global picture with the results from SPS and RHIC at lower energies, as well as to the questions to be addressed in the future. The report covers heavy flavour and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus collisions. Read More

Results from an energy loss model that includes thermal fluctuations in the energy loss for heavy quarks in a strongly-coupled plasma are shown to be qualitatively consistent with single particle data from both RHIC and LHC. The model used is the first to properly include the fluctuations in heavy quark energy loss as derived in string theory and that do not obey the usual fluctuation-dissipation relations. These fluctuations are crucial for simultaneously describing both RHIC and LHC data; leading order drag results without fluctuations are falsified by current data. Read More

We propose a novel definition of a holographic light hadron jet and consider the phenomenological consequences, including the very first fully self-consistent, completely strong-coupling calculation of the jet nuclear modification factor $R_{AA}$, which we find compares surprisingly well with recent preliminary data from LHC. We show that the thermalization distance for light parton jets is an extremely sensitive function of the \emph{a priori} unspecified string initial conditions and that worldsheets corresponding to non-asymptotic energy jets are not well approximated by a collection of null geodesics. Our new string jet prescription, which is defined by a separation of scales from plasma to jet, leads to the re-emergence of the late-time Bragg peak in the instantaneous jet energy loss rate; unlike heavy quarks, the energy loss rate is unusually sensitive to the very definition of the string theory object itself. Read More

We make predictions for the t-differential cross section of exclusive vector meson production (EVMP) in electron-ion collisions, with the aim of comparing DGLAP evolution to CGC models. In the current picture for the high-energy nucleus, nonlinear effects need to be understood in terms of low-$x$ gluon radiation and recombination as well as how this leads to saturation. EVMP grants experimental access to the edge region of the highly-boosted nuclear wavefunction, where the saturation scale for CGC calculations becomes inaccessible to pQCD. Read More

Heavy flavor research is a vigorous and active topic in high-energy QCD physics. Comparing theoretical predictions to data as a function of flavor provides a unique opportunity to tease out properties of quark-gluon plasma. We explicitly demonstrate this utility with energy loss predictions based on the assumption of 1) a weakly-coupled plasma weakly coupled to a high-pT probe using pQCD and 2) a strongly-coupled plasma strongly coupled to a high-pT probe using AdS/CFT; we find that while the former enjoys broad qualitative agreement with data, it is difficult to reconcile the latter with experimental measurements. Read More

Recent LHC data suggest that perturbative QCD provides a qualitatively consistent picture of jet quenching. Constrained to RHIC pi0 suppression, zero parameter WHDG energy loss predictions agree quantitatively with the charged hadron v2 and D meson RAA measured at LHC and qualitatively with the charged hadron RAA. On the other hand, RHIC-constrained LHC predictions from fully strongly-coupled AdS/CFT qualitatively oversuppress D mesons compared to data; light meson predictions are on less firm theoretical ground but also suggest oversuppression. Read More

We compare calculations of jet quenching observables at sqrt s = 2.76 ATeV to preliminary LHC data from weak-coupling pQCD and strong-coupling AdS/CFT drag energy loss models. Rigorously constrained to sqrt s = 200 AGeV RHIC pi^0 suppression data and introducing no free parameters, the pQCD-based WHDG model simultaneously describes qualitatively the suppression of light hadrons and quantitatively the azimuthal anisotropy (over many centrality classes) of light hadrons and the suppression of D mesons at LHC. Read More

**Authors:**D. Boer, M. Diehl, R. Milner, R. Venugopalan, W. Vogelsang, A. Accardi, E. Aschenauer, M. Burkardt, R. Ent, V. Guzey, D. Hasch, K. Kumar, M. A. C. Lamont, Y. Li, W. J. Marciano, C. Marquet, F. Sabatie, M. Stratmann, F. Yuan, S. Abeyratne, S. Ahmed, C. Aidala, S. Alekhin, M. Anselmino, H. Avakian, A. Bacchetta, J. Bartels, H. BC, J. Beebe-Wang, S. Belomestnykh, I. Ben-Zvi, G. Beuf, J. Blumlein, M . Blaskiewicz, A. Bogacz, S. J. Brodsky, T. Burton, R. Calaga, X. Chang, I. O. Cherednikov, P. Chevtsov, G. A. Chirilli, C. Ciofi degli Atti, I. C. Cloet, A. Cooper-Sarkar, R. Debbe, Ya. Derbenev, A. Deshpande, F. Dominguez, A. Dumitru, R. Dupre, B. Erdelyi, C. Faroughy, S. Fazio, A. Fedotov, J. R. Forshaw, R. Geraud, K. Gallmeister, L. Gamberg, J. -H. Gao, D. Gassner, F. Gelis, G. P. Gilfoyle, G. Goldstein, K. Golec-Biernat, V. P. Goncalves, M. Gonderinger, M. Guzzi, P. Hagler, H. Hahn, L. Hammons, Y. Hao, P. He, T. Horn, W. A. Horowitz, M. Huang, A. Hutton, B. Jager, W. Jackson, A. Jain, E. C. Johnson, Z. -B. Kang, L. P. Kaptari, D. Kayran, J. Kewisch, Y. Koike, A. Kondratenko, B. Z. Kopeliovich, Y. V. Kovchegov, G. Krafft, P. Kroll, S. Kumano, K. Kumericki, T. Lappi, T. Lautenschlager, R. Li, Z. -T. Liang, V. N. Litvinenko, S. Liuti, Y. Luo, D. Muller, G. Mahler, A. Majumder, S. Manikonda, F. Marhauser, G. McIntyre, M. Meskauskas, W. Meng, A. Metz, C. B. Mezzetti, G. A. Miller, M. Minty, S. -O. Moch, V. Morozov, U. Mosel, L. Motyka, H. Moutarde, P. J. Mulders, B. Musch, P. Nadel-Turonski, P. Nadolsky, F. Olness, P. N. Ostrumov, B. Parker, B. Pasquini, K. Passek-Kumericki, A. Pikin, F. Pilat, B. Pire, H. Pirner, C. Pisano, E. Pozdeyev, A. Prokudin, V. Ptitsyn, X. Qian, J. -W. Qiu, M. Radici, A. Radyushkin, T. Rao, R. Rimmer, F. Ringer, S. Riordan, T. Rogers, J. Rojo, T. Roser, R. Sandapen, R. Sassot, T. Satogata, H. Sayed, A. Schafer, G. Schnell, P. Schweitzer, B. Sheehy, J. Skaritka, G. Soyez, M. Spata, H. Spiesberger, A. M. Stasto, N. G. Stefanis, M. Strikman, M. Sullivan, L. Szymanowski, K. Tanaka, S. Taneja, S. Tepikian, B. Terzic, Y. Than, T. Toll, D. Trbojevic, E. Tsentalovich, N. Tsoupas, K. Tuchin, J. Tuozzolo, T. Ullrich, A. Vossen, S. Wallon, G. Wang, H. Wang, X. -N. Wang, S. Webb, C. Weiss, Q. Wu, B. -W. Xiao, W. Xu, B. Yunn, A. Zelenski, Y. Zhang, J. Zhou, P. Zurita

This report is based on a ten-week program on "Gluons and the quark sea at high-energies", which took place at the Institute for Nuclear Theory in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics. This report is organized around four major themes: i) the spin and flavor structure of the proton, ii) three-dimensional structure of nucleons and nuclei in momentum and configuration space, iii) QCD matter in nuclei, and iv) Electroweak physics and the search for physics beyond the Standard Model. Read More

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 suppression and LHC charged hadron suppression. Read More

We calculate running coupling corrections for the lowest-order gluon production cross section in high energy hadronic and nuclear scattering using the BLM scale-setting prescription. At leading order there are three powers of fixed coupling; in our final answer, these three couplings are replaced by seven factors of running coupling: five in the numerator and two in the denominator, forming a `septumvirate' of running couplings, analogous to the `triumvirate' of running couplings found earlier for the small-x BFKL/BK/JIMWLK evolution equations. It is interesting to note that the two running couplings in the denominator of the `septumvirate' run with complex-valued momentum scales, which are complex conjugates of each other, such that the production cross section is indeed real. Read More

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'). Read More

We present parameter-free predictions of the nuclear modification factor, R_{AA}^pi(p_T,s), of high p_T pions produced in Pb+Pb collisions at sqrt{s}_{NN}=2.76 and 5.5 ATeV based on the WHDG/DGLV (radiative+elastic+geometric fluctuation) jet energy loss model. Read More

The momentum dependence of the exciting new Pb + Pb data from LHC qualitatively suggests a perturbative picture interpretation for the energy loss of high-pT particles, but conclusions are difficult to draw due to the lack of 1) a quantitative theoretical calculation constrained by current high precision RHIC data and 2) a lack of control p + p and p + Pb data at LHC. Future measurements of identified heavy quark suppression will provide a novel qualitative tool for determining the dominant physics of the quark-gluon plasma created at RHIC and LHC. Read More

We predict readily experimentally measurable differences in the diffractive cross section in the coherent exclusive photoproduction of J/psi mesons in e + A collisions at eRHIC and LHeC energies for nuclear gluon distributions assumed to 1) evolve in x with DGLAP dynamics and have a spatial distribution proportional to the Glauber nuclear thickness function and 2) evolve in x and b according to the KLN prescription of CGC dynamics. We find that CGC physics predicts that the nuclear gluon density widens significantly as a function of x yielding diffractive peaks and minima that evolve dramatically with x; on the other hand the DGLAP Glauber distribution yields peaks and minima constant in x. We also find that the dipole cross section at the level of two gluon exchange within the KLN parameterization of the CGC satisfies the black disk limit whereas this limit is violated when DGLAP evolution is used; the normalization of the diffractive cross section grows more slowly in x by several orders of magnitude when using the KLN parameterization as compared to the result when employing DGLAP evolution. Read More

Focusing on four types of correlation plots, $R_{\rm AA}$ vs. $v_2$, $R_{\rm AA}$ vs. $I_{\rm AA}$, $I_{\rm AA}$ vs. Read More

Despite the 300% systematic theoretical uncertainty associated with extracting qhat using current energy loss models due to the collinear approximation, and despite the uncertainties in the initial geometry and corrections due to the fluctuations in the initial overlap of a heavy ion collision, a simultaneous description of high-pT pi^0 RAA and v2 is not possible with current pQCD-based energy loss models. However a good description of out-of-plane RAA as a function of centrality is possible. Alternatively, energy loss models based on AdS/CFT give a better qualitative description of pi^0 and non-photonic electron RAA as well as high-pT ratios of antiprotons to pi^- production than those based on pQCD. Read More

With the energy scales opened up by RHIC and LHC the age of high-pT physics is upon us. This has created new opportunities and novel mysteries, both of which will be explored in this thesis. The possibility now exists experimentally to exploit these high momentum particles to uniquely probe the unprecedented state of matter produced in heavy ion collisions. Read More

We calculate running coupling corrections for the lowest-order gluon production cross section in high energy hadronic and nuclear scattering using the BLM scale-setting prescription. In the final answer for the cross section the three powers of fixed coupling are replaced by seven factors of running coupling, five in the numerator and two in the denominator, forming a 'septumvirate' of running couplings, analogous to the 'triumvirate' of running couplings found earlier for the small-x BFKL/BK/JIMWLK evolution equations. It is interesting to note that the two running couplings in the denominator of the 'septumvirate' run with complex-valued momentum scales, which are complex conjugates of each other, such that the production cross section is indeed real. Read More

We find that the current radiative energy loss kernels obtained from the opacity expansion dramatically violate the collinear approximation used in their derivation. By keeping only the lowest order in collinearity terms, models based on the opacity expansion have ~50% systematic uncertainty in the calculation of pi^0 R_AA in 0-5% most central RHIC collisions resulting in a systematic uncertainty of ~200% in the extracted medium density. Surprisingly, the inclusion of a thermal gluon mass on the order of the Debye screening scale affects R_AA at only about the 5% level due to non-intuitive coherence effects. Read More

We first note the failures of traditional pQCD techniques as applied to high-pT heavy ion physics and the suggestion of examining the double ratio of charm to bottom nuclear modification factors to generically distinguish between these weak coupling ideas and the strong coupling ideas of AdS/CFT. In order to gain confidence in the use of AdS/CFT (and to increase the likelihood of falsifying it and/or pQCD) we extend its application to heavy quark energy loss in both thermal and nonthermal media by calculating the string drag in a shock metric. Read More

**Authors:**W. A. Horowitz

After an introduction to jet phenomenology and tests of AdS/CFT at LHC we derive the heavy quark drag of a string dangling in a shock metric of AdS space, thus generalizing the AdS/CFT drag calculations in strongly coupled thermal media to momentum loss in both hot and cold nuclear matter. Read More

We calculate the drag force on a heavy quark hit by a shock wave, thus generalizing the strongly coupled AdS/CFT heavy quark drag calculations to both hot and cold nuclear matter. The derivation employs the trailing string configuration, similar to that used in the literature for a quark moving through a thermal medium, though in the shock metric the string profile is described by a much simpler analytic function. Our expression for the drag depends on the typical transverse momentum scale of the matter in the shock. Read More

We calculate the 0th order in opacity number distribution of massive photons (gluons) for heavy quark production radiation including interference from the away-side jet. While consistent with the soft photon (gluon) approximation, we find that approximating 1-x with 1, as done in previous calculations, strongly affects the magnitude of energy loss. Restoring gauge invariance by including the radiation associated with the away-side jet fills in the "dead cone," but is a relatively small effect. Read More

We present charm and bottom nuclear modification factors for RHIC and LHC using Standard Model perturbative QCD and recent AdS/CFT string drag energy loss models. We find that extreme extrapolations to LHC mask potential experimentally determinable differences in the individual $R_{AA}$s but that their ratio, $R_{AA}^c/R_{AA}^b$ as a function of transverse momentum is a remarkably robust observable for finding deviations from either theoretical framework. Read More

**Authors:**S. Abreu, S. V. Akkelin, J. Alam, J. L. Albacete, A. Andronic, D. Antonov, F. Arleo, N. Armesto, I. C. Arsene, G. G. Barnafoldi, J. Barrette, B. Bauchle, F. Becattini, B. Betz, M. Bleicher, M. Bluhm, D. Boer, F. W. Bopp, P. Braun-Munzinger, L. Bravina, W. Busza, M. Cacciari, A. Capella, J. Casalderrey-Solana, R. Chatterjee, L. -W. Chen, J. Cleymans, B. A. Cole, Z. Conesa Del Valle, L. P. Csernai, L. Cunqueiro, A. Dainese, J. Dias de Deus H. -T. Ding, M. Djordjevic, H. Drescher, I. M. Dremin A. Dumitru, A. El, R. Engel, D. d'Enterria, K. J. Eskola, G. Fai, E. G. Ferreiro, R. J. Fries, E. Frodermann, H. Fujii, C. Gale, F. Gelis, V. P. Goncalves, V. Greco, C. Greiner, M. Gyulassy, H. van Hees, U. Heinz, H. Honkanen, W. A. Horowitz, E. Iancu, G. Ingelman, J. Jalilian-Marian, S. Jeon, A. B. Kaidalov, B. Kampfer, Z. -B. Kang, Iu. A. Karpenko, G. Kestin, D. Kharzeev, C. M. Ko, B. Koch, B. Kopeliovich, M. Kozlov, I. Kraus, I. Kuznetsova, S. H. Lee, R. Lednicky, J. Letessier, E. Levin, B. -A. Li, Z. -W. Lin, H. Liu, W. Liu, C. Loizides, I. P. Lokhtin, M. V. T. Machado, L. V. Malinina, A. M. Managadze, M. L. Mangano, M. Mannarelli, C. Manuel, G. Martinez, J. G. Milhano, A. Mocsy, D. Molnar, M. Nardi, J. K. Nayak, H. Niemi, H. Oeschler, J. -Y. Ollitrault, G. Paic, C. Pajares, V. S. Pantuev, G. Papp, D. Peressounko, P. Petreczky, S. V. Petrushanko, F. Piccinini, T. Pierog, H. J. Pirner, S. Porteboeuf, I. Potashnikova, G. Y. Qin, J. -W. Qiu, J. Rafelski, K. Rajagopal, J. Ranft, R. Rapp, S. S. Rasanen, J. Rathsman, P. Rau, K. Redlich, T. Renk, A. H. Rezaeian, D. Rischke, S. Roesler, J. Ruppert, P. V. Ruuskanen, C. A. Salgado, S. Sapeta, I. Sarcevic, S. Sarkar, L. I. Sarycheva, I. Schmidt, A. I. Shoshi, B. Sinha, Yu. M. Sinyukov, A. M. Snigirev, D. K. Srivastava, J. Stachel, A. Stasto, H. Stocker, C. Yu. Teplov, R. L. Thews, G. Torrieri, V. Topor Pop, D. N. Triantafyllopoulos, K. L. Tuchin, S. Turbide, K. Tywoniuk, A. Utermann, R. Venugopalan, I. Vitev, R. Vogt, E. Wang, X. N. Wang, K. Werner, E. Wessels, S. Wheaton, S. Wicks, U. A. Wiedemann, G. Wolschin, B. -W. Xiao, Z. Xu, S. Yasui, E. Zabrodin, K. Zapp, B. Zhang, B. -W. Zhang, H. Zhang, D. Zhou

This writeup is a compilation of the predictions for the forthcoming Heavy Ion Program at the Large Hadron Collider, as presented at the CERN Theory Institute 'Heavy Ion Collisions at the LHC - Last Call for Predictions', held from May 14th to June 10th 2007. Read More

We predict the charm and bottom quark nuclear modification factors using weakly coupled pQCD and strongly coupled AdS/CFT drag methods. The log(pT/M_Q)/pT dependence of pQCD loss and the momentum independence of drag loss lead to different momentum dependencies for the R_{AA} predictions. This difference is enhanced by examining a new experimental observable, the double ratio of charm to bottom nuclear modification factors, R^{cb}=R^c_{AA}/R^b_{AA}. Read More

LHC predictions for the charm and bottom nuclear modification factors using pQCD and AdS/CFT drag energy loss models are given. We show that a new observable, the double ratio of charm to bottom nuclear modification factors, allows for easy experimental distinction between the two classes of energy loss models. Read More

Heavy quark jet quenching in nuclear collisions at LHC is predicted and compared using the classical gravity AdS/CFT correspondence and Standard Model perturbative QCD. The momentum independence and inverse quark mass dependence of the drag coefficient in AdS/CFT differs substantially from the characteristic log(pT/M)/pT variation of the drag in QCD. We propose that the measurement of the momentum dependence of the double ratio of the nuclear modification factors of charm and bottom jets is a robust observable that can be used to search for strong coupling deviations from perturbative QCD predictions. Read More

We present the LHC predictions for the WHDG model of radiative, elastic, and path length fluctuating energy loss. We find the pT dependence of RAA is qualitatively very different from AWS-based energy loss extrapolations to the LHC; the large pT reach of the year one data at the LHC should suffice to distinguish between the two. We also discuss the importance of requiring a first elastic scatter before any medium-induced elastic or radiative loss occurs, a necessary physical effect not considered in any previous models. Read More

We examine the sensitivity and surface bias of convolved DGLV radiative and elastic loss in a realistic geometry including Bjorken expansion. We find that this more faithful treatment of the medium density is not a priori reproducible via fixed length approximations, and neither the fragility nor the surface emission of BDMPS-based models is seen. Read More

We calculate the collisional energy loss suffered by a heavy (charm) quark created at a finite time within a Quark Gluon Plasma (QGP) in the classical linear response formalism as in Peigne {\it et al.} \cite{peigne}. We pay close attention to the problem of formulating a suitable current and the isolation of binding and radiative energy loss effects. Read More

We propose a possible perturbative QCD solution to the heavy quark tomography problem posed by recent non-photonic single electron data from central Au+Au collisions at $\sqrt{s} = 200$ AGeV. Jet quenching theory is extended to include (1) elastic as well as (2) inelastic parton energy losses and (3) jet path length fluctuations. The three effects combine to reduce the discrepancy between theory and the data without violating the global entropy bounds from multiplicity and elliptic flow data. Read More

We present a new plot for representing RAA data that emphasizes the strong correlation between high-pt suppression and its elliptic anisotropy. We demonstrate that existing models cannot reproduce the centrality dependence of this correlation. Modification of a geometric energy loss model to include thermal absorption and stimulated emission can match the trend of the data, but requires dN/dy values inconsistent with the observed multiplicity. Read More