Proton-proton multiplicity distributions at LHC and the Pomeron intercept

We compute the proton-proton multiplicity distributions at LHC energies in the framework of a multiple scattering model assuming a Poisson distribution for each inelastic collision. Multiple scattering is essential to broaden the multiplicity distribution. We obtain approximate KNO scaling for small pseudo-rapidity intervals ($|\eta | < 0.5$) and sizable KNO scaling violations for larger ones, in agreement with experiment.Comment: 6 pages, 2 figure

Multiplicities and J/ψJ/\psi suppression at LHC energies

We present our predictions on multiplicities and $J/\psi$ suppression at LHC energies. Our results take into account shadowing effects in the initial state and final state interactions with the hot medium. We obtain 1800 charged particles at LHC and the $J/\psi$ suppression increases by a factor 5 to 6 compared to RHIC.Comment: 2 pages, 2 figures. Contributed to Workshop on Heavy Ion Collisions at the LHC: Last Call for Predictions, Geneva, Switzerland, 14 May - 8 Jun 200

Elliptic Flow in a Final State Interaction Model

We propose a final state interaction model to describe the fixed $p_T$ suppression of the yield of particles at all values of $p_T$. We make an extension of the model to the motion in the transverse plane which introduces a dependence of the suppression on the azimuthal angle $\theta_R$. We obtain values of the elliptic flow $v_{2}$ close to the experimental ones for all values of $p_T$.Comment: 4 pages, 6 figures, proceedings of XLIst Rencontres de Moriond: QCD and Hadronic Interactions at high energ

Radial Flow in a Final State Interaction Model

In the framework of a final state interaction model, we show that the so-called radial flow, i.e. the almost linear increase of the inverse slope $T$ with the mass of the produced particle, is already contained in the initial condition -- with a slope $$ (the so-called strength of the average radial transverse flow) which is larger than the measured one. While the precise value of the slope depends on the details of the model, the above result has a very general basis -- namely the increase with increasing $p_T$ of the fixed $p_T$ suppression, in the low $p_T$ region.Comment: 9 pages, 2 figure

Large transverse momentum suppression at RHIC: Shadowing and absorption

We propose a model of suppression of $\pi^0$'s based on two different effects: at low $p_T$ we take into account the shadowing corrections, which are non-linear and essential for the description of the inclusive spectra, while at large $p_T$ the suppression is produced through the interaction of the large $p_T$ pion with the dense medium created in the collision. The main features of the data on $AuAu$ and $dAu$ collisions at RHIC energies are reproduced both at mid and at forward rapidities.Comment: 6 pages, 2 figures. Contribution to the 8th Workshop on Non-Perturbative Quantum Chromodynamics, June 7-11, 2004, l'Institut Astrophysique de Paris, Franc

Frustration in Biomolecules

Biomolecules are the prime information processing elements of living matter. Most of these inanimate systems are polymers that compute their structures and dynamics using as input seemingly random character strings of their sequence, following which they coalesce and perform integrated cellular functions. In large computational systems with a finite interaction-codes, the appearance of conflicting goals is inevitable. Simple conflicting forces can lead to quite complex structures and behaviors, leading to the concept of "frustration" in condensed matter. We present here some basic ideas about frustration in biomolecules and how the frustration concept leads to a better appreciation of many aspects of the architecture of biomolecules, and how structure connects to function. These ideas are simultaneously both seductively simple and perilously subtle to grasp completely. The energy landscape theory of protein folding provides a framework for quantifying frustration in large systems and has been implemented at many levels of description. We first review the notion of frustration from the areas of abstract logic and its uses in simple condensed matter systems. We discuss then how the frustration concept applies specifically to heteropolymers, testing folding landscape theory in computer simulations of protein models and in experimentally accessible systems. Studying the aspects of frustration averaged over many proteins provides ways to infer energy functions useful for reliable structure prediction. We discuss how frustration affects folding, how a large part of the biological functions of proteins are related to subtle local frustration effects and how frustration influences the appearance of metastable states, the nature of binding processes, catalysis and allosteric transitions. We hope to illustrate how Frustration is a fundamental concept in relating function to structural biology.Comment: 97 pages, 30 figure

J/psi suppression at SPS and RHIC in the comovers approach

The NA50 collaboration data on the $J/\psi$ suppression are compared with the results obtained in a comovers approach based on the Dual Parton Model (DPM). Predictions for the $J/\psi$ suppression versus the charged multiplicity - measured in the rapidity region of the dimuon trigger - are given for SPS and RHIC energies.Comment: 4 pages, contribution to QM200