Photon-tagged correlations in heavy-ion collisions: kinematic requirements and a case study

Photon-tagged correlations may be useful to determine how the dense partonic medium produced in heavy-ion collisions affects the fragmentation of high-energy quarks and gluons into a leading hadron. In these proceedings, I discuss the kinematic requirements for the hadron and the prompt photon transverse momentum cuts. A case study at LHC energy, tagging on p_T > 20 GeV and p_T > 50 GeV photons, is then briefly examined.Comment: 4 pages, 2 figures. To appear in the proceedings of the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (QM2006), Shanghai, China, 14-20 November 200

Quarkonium suppression in heavy-ion collisions from coherent energy loss in cold nuclear matter

The effect of parton energy loss in cold nuclear matter on the suppression of quarkonia (J/psi, Upsilon) in heavy-ion collisions is investigated, by extrapolating a model based on coherent radiative energy loss recently shown to describe successfully J/psi and Upsilon suppression in proton-nucleus collisions. Model predictions in heavy-ion collisions at RHIC (Au-Au, Cu-Cu, and Cu-Au) and LHC (Pb-Pb) show a sizable suppression arising from the sole effect of energy loss in cold matter. This effect should thus be considered in order to get a reliable baseline for cold nuclear matter effects in quarkonium suppression in heavy-ion collisions, in view of disentangling hot from cold nuclear effects.Comment: 20 pages, 9 figure

Heavy-quarkonium suppression in p-A collisions from parton energy loss in cold QCD matter

The effects of parton energy loss in cold nuclear matter on heavy-quarkonium suppression in p-A collisions are studied. It is shown from first principles that at large quarkonium energy E and small production angle in the nucleus rest frame, the medium-induced energy loss scales as E. Using this result, a phenomenological model depending on a single free parameter is able to reproduce J/psi and Upsilon suppression data in a broad xF-range and at various center-of-mass energies. These results strongly support energy loss as the dominant effect in heavy-quarkonium suppression in p-A collisions. Predictions for J/psi and Upsilon suppression in p-Pb collisions at the LHC are made. It is argued that parton energy loss scaling as E should generally apply to hadron production in p-A collisions, such as light hadron or open charm production.Comment: 41 pages, 21 figures, 4 tables. v2: Model corrected at small and negative xF (section 3.1), conclusions unchange

Quarkonium suppression from coherent energy loss in fixed-target experiments using LHC beams

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/$\psi$ and $\Upsilon$ as a function of rapidity are computed in p-A collisions at $\sqrt{s}=114.6$ GeV, and in p-Pb and Pb-Pb collisions at $\sqrt{s}=72$ GeV. These center-of-mass energies correspond to the collision on fixed-target nuclei of 7 TeV protons and 2.76 TeV lead nuclei available at the LHC.Comment: 7 pages, 2 figure

Coherent medium-induced gluon radiation in hard forward 1→11\to 1 partonic processes

We revisit the medium-induced coherent radiation associated to hard and forward (small angle) scattering of an energetic parton through a nuclear medium. We consider all $1\to 1$ hard forward processes ($g \to g$, $q \to q$, $q \to g$ and $g \to q$), and derive the energy spectrum of induced coherent radiation rigorously to all orders in the opacity expansion and for the specific case of a Coulomb scattering potential. We obtain a simple general formula for the induced coherent spectrum, which encompasses the results corresponding to previously known special cases.Comment: 35 pages, 10 figures; title changed, introduction developed and references added, detailed discussion added in Section VI, all results unchanged; version v2 corresponds to the published versio

Depletion of atmospheric neutrino fluxes from parton energy loss

The phenomenon of fully coherent energy loss (FCEL) in the collisions of protons on light ions affects the physics of cosmic ray air showers. As an illustration, we address two closely related observables: hadron production in forthcoming proton-oxygen collisions at the LHC, and the atmospheric neutrino fluxes induced by the semileptonic decays of hadrons produced in proton-air collisions. In both cases, a significant nuclear suppression due to FCEL is predicted. The conventional and prompt neutrino fluxes are suppressed by $\sim 10...25\%$ in their relevant neutrino energy ranges. Previous estimates of atmospheric neutrino fluxes should be scaled down accordingly to account for FCEL.Comment: 5 pages, 4 figure

Higher-Twist Dynamics in Large Transverse Momentum Hadron Production

A scaling law analysis of the world data on inclusive large-pT hadron production in hadronic collisions is carried out. A significant deviation from leading-twist perturbative QCD predictions at next-to-leading order is reported. The observed discrepancy is largest at high values of xT=2pT/sqrt(s). In contrast, the production of prompt photons and jets exhibits the scaling behavior which is close to the conformal limit, in agreement with the leading-twist expectation. These results bring evidence for a non-negligible contribution of higher-twist processes in large-pT hadron production in hadronic collisions, where the hadron is produced directly in the hard subprocess rather than by gluon or quark jet fragmentation. Predictions for scaling exponents at RHIC and LHC are given, and it is suggested to trigger the isolated large-pT hadron production to enhance higher-twist processes.Comment: 5 pages, 4 figures. Extended introduction, additional reference

Heavy-quarkonium interaction in QCD at finite temperature

We explore the temperature dependence of the heavy-quarkonium interaction based on the Bhanot-Peskin leading order perturbative QCD analysis. The Wilson coefficients are computed solving the Schrodinger equation in a screened Coulomb heavy-quark potential. The inverse Mellin transform of the Wilson coefficients then allows for the computation of the 1S and 2S heavy-quarkonium gluon and pion total cross section at finite screening/temperature. As a phenomenological illustration, the temperature dependence of the 1S charmonium thermal width is determined and compared to recent lattice QCD results.Comment: 14 pages, 5 figures. Clarification added, published versio

Guo Song tao's Westernization Thought under the context of Hu Nan neo-Confucianism

晚清时期的洋务运动是中国近代化过程中一个重要的转折点。其中，在湖湘理学熏陶下的一批士大夫在其中起到了举足轻重的作用。对于其思想的研究也是我们政治学的一个重点，其中的经验教训对于当代中国的实际运作息息相关，有着很强的借鉴作用。本文将从同时经历了道光、同治、咸丰、光绪四朝的晚清洋务派重将——郭嵩焘出发，重点论述其在固有的湖湘理学中对于当时时局的判断和见解，及对于洋务运动的理论设计，力图对其思想做一个较为清晰和中肯的分析，以达到“窥一豹”而“知全局”的目的。The Westernization Movement in the late Qing Dynasty was a major turning point in China’s Modernization. Especially, under the influence of Hu Nan neo-Confucianism, a group of intellectual played a pivotal role in this period. The research concerning its idealism is also a key in Politics. Its experience and lesson which has strong reference are closely related with the contemporary China's actual...学位：法学硕士院系专业：公共事务学院政治学系_政治学理论学号：1382008115098