abstract

Identifying the accelerators that produce the Galactic and extragalactic cosmic rays has been a priority mission of several generations of high energy gamma ray and neutrino telescopes; success has been elusive so far. Detecting the gamma ray and neutrino fluxes associated with cosmic rays reaches a new watershed with the completion of IceCube, the first neutrino detector with sensitivity to the anticipated fluxes, and the construction of CTA, a ground-based gamma-ray detector that will map and study candidate sources with unprecedented precision. In this paper, we revisit the prospects for revealing the sources of the cosmic rays by a multiwavelength approach; after reviewing the methods, we discuss supernova remnants, gamma-ray bursts, active galaxies and GZK neutrinos in some detail.

abstract

An updated formulation of the soft Pomeron, in which \(s\) and \(t\) channel unitarity screenings are included, is reviewed. The consequent soft scattering features are explored. A summary of the cross-section outputs of the leading groups active in this research are presented including also the calculated values of the gap survival probabilities, which is relevant, mostly, to hard diffractive processes. A utilization of pQCD in soft Pomeron formulation based on Gribov’s Reggeon calculus is applied in the GLM model. The output parameters are compatible with AdS/CFT correspondence. The interplay between Pomeron theory and its corresponding data analysis is discussed. LHC soft scattering data is quoted and compared with theoretical predictions. Its implications for the Pomeron model are discussed.

abstract

In this contribution I want to discuss three phenomena, where effects of fluctuations are very important, multiplicity distributions, diffractive excitation, and nucleus collisions.

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In this paper I discuss the dynamics of particle production in high energy reactions. It includes parton cascades and hadronization in \(e^+e^-\)-an- nihilation, small \(x\) evolution including the Double Leading Log approximation and the BFKL equation, saturation at high densities and the BK equation, and finally the Lund Dipole Cascade model for high energy collisions, which is implemented in the DIPSY MC.

abstract

The transverse structure of the nucleon as probed in hard exclusive processes plays critical role in the understanding of the structure of the underlying event in hard collisions at the LHC, and multiparton interactions. We summarize results of our recent studies of manifestation of transverse nucleon structure in the hard collisions at the LHC, new generalized parton distributions involved in multiparton interactions, presence of parton fluctuations. The kinematic range where interaction of fast partons of the projectile with the target reach black disk regime (BDR) strength is estimated. We demonstrate that in the BDR postselection effect leads to effective fractional energy losses. This effect explains regularities of the single and double forward pion production in \(d\)Au collisions at RHIC and impacts on the forward physics in \(pp\) collisions at the LHC.

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In a very short time the experiments at the LHC have collected a large amount of data that can be used to study minimum bias (MB) collisions and the underlying event (UE) in great detail. The CDF PYTHIA \(6.2\) Tune DW predictions for the LHC UE data at \(900\) GeV and \(7\) TeV are examined in detail. The behavior of the UE at the LHC is roughly what we expected. The LHC PYTHIA \(6.4\) Tune Z1 does an excellent job describing the LHC UE data. The modeling of MB (i.e. the overall inelastic cross-section) is more complicated because one must include a model of diffraction. The ability of PYTHIA Tune DW and Tune Z1 to simultaneously describe both the UE in a hard scattering process and MB collisions are studied. No model describes perfectly all the features of MB collisions at the LHC.

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The CMS soft QCD results in proton–proton collisions at different LHC centre-of-mass energies are reviewed. The first part of the review focuses on the basic kinematic measurements of charged tracks and identified hadrons in minimum bias proton–proton interactions. The second part reports the short- and long-range correlation studies with emphasis on the results exploiting a special trigger specifically developed for large multiplicity events. The third part concentrates on the underlying event phenomenology in jet and Drell–Yan events. Some relevant highlights from the CMS heavy ion program are also discussed.

abstract

Soft QCD contributes to all observables at the LHC, due to the presences of underlying event (UE) and pile-up in all events. Both these processes are dominated by multi-parton interactions (MPI), i.e. the result of proton collisions containing more than one partonic interaction due to collective and beam remnant effects. While there is undoubtedly interesting physics involved in MPI, the primary interest of LHC experiments is to characterise and model the behaviour of UE and pile-up sufficiently well that their influence may be cleanly subtracted in the process of searching for new physics signatures at 7 TeV and beyond. I summarise the soft QCD measurements made by ATLAS using the 2010 and early 2011 datasets, and the use of this data to improve Monte Carlo generator models of MPI for use in forthcoming simulation campaigns.

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We present a pedagogical introduction to the theoretical framework of the Color Glass Condensate (CGC) and the McLerran–Venugopalan (MV) model. We discuss the application of the MV model to describe the early-time dynamics of the relativistic heavy-ion collision. Without longitudinal fluctuations the classical time evolution maintains boost invariance, while an instability develops once fluctuations that break boost invariance are included. We show that this “Glasma instability” enhances rapidity-dependent variations as long as self-interactions among unstable modes stay weak and the system resides in the linear regime. Eventually the amplitude of unstable modes becomes so large that the growth of instability gets saturated. In this non-linear regime the numerical simulations of the Glasma lead to turbulent energy flow from low-frequency modes to higher-frequency modes, which results in a characteristic power-law spectrum. The power found in numerical simulation of the expanding Glasma system turns out to be consistent with Kolmogorov’s \(-5/3\) scaling.

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I discuss two topics of importance to phenomenological applications of perturbative high energy evolution. In the first part I discuss a mechanism which leads to long range rapidity and angular correlations in particle production in dense environment. I argue that positive angular correlations are leading \(1/N_c\) effect and may be responsible for the “ridge” structure observed in high multiplicity \(p\)–\(p\) collisions at LHC. In the second part I describe the setup for calculation of particle production at high transverse momenta and high energy, which fully takes into account the perturbative saturation effects and the leading twist physics. Here I note that recent calculations of inclusive particle production within the high energy approach are missing a term due to inelastic scattering of projectile partons. This piece has to be included in order that the results have proper perturbative limit. Its inclusion is expected to affect strongly the high momentum tail of the particle spectrum.

abstract

A conjecture, in 1999–2001 papers by R. Janik and the author, concerns the holographic description of two-body amplitudes at high energy in terms of AdS/CFT correspondence and more general Gauge/Gravity duality. It states that those amplitudes are related to the helicoidal geometry in the Euclidean version of the gravity duals. The purpose of this paper is a test of this conjecture and the subsequent derivation of the Regge behaviour of these amplitudes using the recent progresses in AdS/CFT correspondence and its extension to non-conformal Gauge/Gravity duality. In Section 1, we provide a test of the conjecture by comparing, after analytic continuation from Euclidean to Minkowski space-time, the prediction for the \(logarithmic\) Regge trajectory for elastic two-quark amplitude with the one obtained from the Alday–Maldacena 2007 solution for the two-gluon amplitude. In Section 2, we derive the high-energy quark–antiquark exchange (Reggeon) amplitude in the context of Gauge/Gravity duality for a generic confining case. By a suitable analytic continuation, we confirm the prediction of linear Regge trajectories obtained in the original papers and derive new results on the exchanged quark mass dependence of the reggeon amplitude. The new material contained in the paper comes from a collaboration with Matteo Giordano and Shigenori Seki.

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In this paper, the basics of finite temperature lattice QCD are summarised. At high temperatures there is a transition from a state dominated by colourless hadrons to a state dominated by coloured particles. The nature of this transition is determined to be an analytic cross-over. The absolute scale (the transition temperature \(T_{\rm c}\)) is calculated for various observables. Finally, the equation of state of the strongly interacting matter is presented.

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We analyze the elliptic flow parameter \(v_{2}\) in Pb+Pb collisions at the LHC energy using a hybrid model in which the evolution of the quark-gluon plasma is described by ideal hydrodynamics and the subsequent hadronic stage by a hadron cascade model. For initial conditions, we employ Monte Carlo versions of the Glauber and the Kharzeev–Levin–Nardi models and compare results with each other. We demonstrate that the differential elliptic flow \(v_2(p_{\rm T})\) does not change so much when the collision energy increases, whereas the integrated \(v_2\) increases due to the enhancement of mean transverse momentum.

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A status report of utilizing soft electromagnetic radiation (aka thermal photons and dileptons) in the diagnosis of strongly interacting matter in ultrarelativistic heavy-ion collisions is given. After briefly elaborating on relations of the electromagnetic spectral function to chiral symmetry restoration and the transition from hadron to quark degrees of freedom, various calculations of electromagnetic emission rates in the hadronic and quark-gluon plasma phases of QCD matter are discussed. This, in particular, includes insights from recent thermal lattice QCD computations. Applications to dilepton and photon spectra in heavy-ion collisions highlight their role as a spectro-, thermo-, baro- and chrono-meter of extraordinary precision.

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In this paper, we discuss physics of dense matter, which are expected to happen inside compact stars such as neutron stars. After the general introduction to basic properties of dense hadronic and quark matter as well as compact stars, we first focus on QCD phase transitions and its phase structures, based on the Ginzburg–Landau analysis. Then, we show some astrophysical applications into neutron star phenomena such as equation of state, cooling and gravitational wave radiation and some recent developments.