12,905 research outputs found

    Energy flow between jets in the kt algorithm

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    We consider the impact of the kt algorithm on energy flow into gaps between jets in any QCD hard process. While we confirm the observation that the kt clustering procedure considerably reduces the impact of non-global logarithms, we unearth yet new sources of logarithmic enhancement, that stem from using the ktk_t algorithm to define the final state. We comment on the nature of the logarithms we find and discuss their all-orders treatment.Comment: 4 pages, submitted to the proceedings of DIS 2006, Tsukuba, Japa

    Phase Diagram of a Classical Fluid in a Quenched Random Potential

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    We consider the phase diagram of a classical fluid in the presence of a random pinning potential of arbitrary strength. Introducing replicas for averaging over the quenched disorder, we use the hypernetted chain approximation to calculate the correlations in the replicated liquid. The freezing transition of the liquid into a nearly crystalline state is studied using a density functional approach, and the liquid-to-glass transition is studied using a phenomenological replica symmetry breaking approach introduced by Mezard and Parisi. The first-order liquid-to-crystal transition is found to change to a continuous liquid-to-glass transition as the strength of the disorder is increased above a threshold value.Comment: 7 pages, 4 figures, to appear in EuroPhysics Letter

    Aspects of power corrections in hadron-hadron collisions

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    The program of understanding inverse-power law corrections to event shapes and energy flow observables in e+ e- annihilation to two jets and DIS (1+1) jets has been a significant success of QCD phenomenology over the last decade. The important extension of this program to similar observables in hadron collisions is not straightforward, being obscured by both conceptual and technical issues. In this paper we shed light on some of these issues by providing an estimate of power corrections to the inter-jet E_t flow distribution in hadron collisions using the techniques that were employed in the e+ e- annihilation and DIS cases.Comment: 15 pages, 1 figure, uses JHEP3.cl

    Resummation of the jet broadening in DIS

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    We calculate the leading and next-to-leading logarithmic resummed distribution for the jet broadening in deep inelastic scattering, as well as the power correction for both the distribution and mean value. A truncation of the answer at NLL accuracy, as is standard, leads to unphysical divergences. We discuss their origin and show how the problem can be resolved. We then examine DIS-specific procedures for matching to fixed-order calculations and compare our results to data. One of the tools developed for the comparison is an NLO parton distribution evolution code. When compared to PDF sets from MRST and CTEQ it reveals limited discrepancies in both.Comment: 48 pages, 7 figure

    Problems in resumming interjet energy flows with k_t clustering

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    We consider the energy flow into gaps between hard jets. It was previously believed that the accuracy of resummed predictions for such observables can be improved by employing the ktk_t clustering procedure to define the gap energy in terms of a sum of energies of soft jets (rather than individual hadrons) in the gap. This significantly reduces the sensitivity to correlated soft large-angle radiation (non-global leading logs), numerically calculable only in the large NcN_c limit. While this is the case, as we demonstrate here, the use of ktk_t clustering spoils the straightforward single-gluon Sudakov exponentiation that multiplies the non-global resummation. We carry out an O(αs2){\mathcal{O}}(\alpha_s^2) calculation of the leading single-logarithmic terms and identify the piece that is omitted by straightforward exponentiation. We compare our results with the full O(αs2){\mathcal{O}} (\alpha_s^2) result from the program EVENT2 to confirm our conclusions. For e+e−→2e^{+}e^{-} \to 2 jets and DIS (1+1) jets one can numerically resum these additional contributions as we show, but for dijet photoproduction and hadron-hadron processes further studies are needed.Comment: 11 pages, 5 figure

    Fusion and breakup in the reactions of 6,7Li and 9Be

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    We develop a three body classical trajectory Monte Carlo (CTMC) method to dicsuss the effect of the breakup process on heavy-ion fusion reactions induced by weakly bound nuclei. This method follows the classical trajectories of breakup fragments after the breakup takes place, and thus provides an unambiguous separation between complete and incomplete fusion cross sections. Applying this method to the fusion reaction 6^{6}Li + 209^{209}Bi, we find that there is a significant contribution to the total complete fusion cross sections from the process where all the breakup fragments are captured by the target nucleus (i.e., the breakup followed by complete fusion).Comment: 4 pages, 3 eps figures. Uses espcrc1.sty. To be published in the proceedings of the 8th international conference on clustering aspects of nuclear structure and dynamics, November 24 - 29, 2003, Nara, Japan (Nucl. Phys. A

    On the universality of hadronisation corrections to QCD jets

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    We improve previously derived analytical estimates of hadronisation corrections to QCD jets at hadron colliders, firmly establishing at the two-loop level the link to the well-known power corrections to LEP event-shape variables. The results of this paper apply to jets defined in the kt and anti-kt algorithms but the general framework presented here holds also for other algorithms for which calculations are in progress.Comment: 28 pages, 3 tables, 1 figure, uses JHEP3.cl

    On large angle multiple gluon radiation

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    Jet shape observables which involve measurements restricted to a part of phase space are sensitive to multiplication of soft gluon with large relative angles and give rise to specific single logarithmically enhanced (SL) terms (non-global logs). We consider associated distributions in two variables which combine measurement of a jet shape V in the whole phase space (global) and that of the transverse energy flow away from the jet direction, Eout (non-global). We show that associated distributions factorize into the global distribution in V and a factor that takes into account SL contributions from multi-gluon ``hedgehog'' configurations in all orders. The latter is the same that describes the single-variable Eout distribution, but evaluated at a rescaled energy VQ.Comment: 16 page