Statistical Physics and Light-Front Quantization

Raufeisen, Joerg

doi:10.2172/829750

Cited by 3 publications

(3 citation statements)

References 28 publications

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“…For convenience, the factor exp(−iq min L (z 2 − z 1 )) describing the longitudinal motion is included into the Green function G( ρ 2 , z 2 | ρ 1 , z 1 ) as was proposed in Ref. [22].…”

Section: Drell-yan Process In Pa Collisions: the Green Function mentioning

confidence: 99%

Drell-Yan process in pA collisions: Path-integral treatment of coherence effects

et al. 2016

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In this work, we investigate production of Drell-Yan (DY) pairs in proton-nucleus collisions in kinematic regions where the corresponding coherence length does not exceed the nuclear radius, RA, and the quantum coherence effects should be treated with a special care. The results for the nucleusto-nucleon production ratio available in the literature so far are usually based on the assumption of a very long coherence length (LCL) lc ≫ RA. Since the onset of coherence effects is controlled by the coherence length lc, we estimated its magnitude in various kinematic regions of the DY process and found that the LCL approximation should not be used at small and medium c.m. collision energies ( √ s 200 GeV) as well as at large dilepton invariant masses. In order to obtain realistic predictions, we computed for the first time the DY cross section using the generalised color dipole approach based on the rigorous Green function formalism, which naturally incorporates the color transparency and quantum coherence effects and hence allows to estimate the nuclear shadowing with no restrictions on the CL. In addition to the shadowing effect, we studied a complementary effect of initial state interactions (ISI) that causes an additional suppression at large values of the Feynman variable. Numerical results for the nuclear modification factor accounting for the ISI effect and the finite lc are compared to the data available from the fixed-target FNAL measurements and a good agreement has been found. Besides, we present new predictions for the nuclear suppression as a function of dilepton rapidity and invariant mass in the kinematic regions that can be probed by the RHIC collider as well as by the planned AFTER@LHC and LHCb fixed-target experiments. I. INTRODUCTIONHadronic production of massive lepton pairs, known as the Drell-Yan (DY) process, is a clean, precise and controllable probe for short-distance dynamics and partonic structure of hadrons (for a recent review see, e.g. Ref.[1]). In particular, the DY process on nuclear targets is an ideal tool to probe and to quantify the initial state interaction (ISI), saturation, gluon shadowing and coherence effects in a clean environment due to the absence of final-state interactions and fragmentation processes typically associated with energy loss or absorption phenomena [2]. The corresponding predictions for the nucleus-to-nucleon ratio known as the nuclear modification factor R pA have been obtained using the color dipole approach [3][4][5][6][7][8][9][10][11][12][13] which is known to provide as precise predictions for the DY cross section in pp collisions as the Next-to-Leading-Order (NLO) collinear factorisation framework. In the color dipole picture, the DY process off nuclei looks as γ * Bremsstrahlung off a projectile quark propagating through the nuclear medium [6]. Remarkably, the dipole framework enables us to include the coherence effects in nuclear collisions naturally from the first principles by means of the generalised path-integral (or Green function) formulation (se...

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Section: Drell-yan Process In Pa Collisions: the Green Function mentioning

confidence: 99%

Drell-Yan process in pA collisions: Path-integral treatment of coherence effects

et al. 2016

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“…A remarkable feature of deep inelastic lepton-proton scattering at HERA is that approximately 10% events are diffractive [184,185,186]: the target proton remains intact and there is a large rapidity gap between the proton and the other hadrons in the final state. These diffractive deep inelastic scattering (DDIS) events can be understood most simply from the perspective of the color-dipole model [187]: the qq Fock state of the high-energy virtual photon diffractively dissociates into a diffractive dijet system. The color-singlet exchange of multiple gluons between the color dipole of the qq and the quarks of the target proton leads to the diffractive final state.…”

Section: The Paradox Of Diffractive Deep Inelastic Scatteringmentioning

confidence: 99%

Light-Front QCD

Brodsky¹

2004

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In these lectures, I survey a number of applications of light-front methods to hadron and nuclear physics phenomenology and dynamics, including light-front statistical physics. Light-front Fock-state wavefunctions provide a frame-independent representation of hadrons in terms of their fundamental quark and gluon degrees of freedom. Nonperturbative methods for computing LFWFs in QCD are discussed, including string/gauge duality which predicts the power-law fall-off at high momentum transfer of light-front Fock-state hadronic wavefunctions with an arbitrary number of constituents and orbital angular momentum. The AdS/CFT correspondence has important implications for hadron phenomenology in the conformal limit, including an all-orders derivation of counting rules for exclusive processes. One can also compute the hadronic spectrum of near-conformal QCD assuming a truncated AdS/CFT space. Given the LFWFs, one can compute form factors, heavy hadron decay amplitudes, hadron distribution amplitudes, and the generalized parton distributions underlying deeply virtual Compton scattering. The quantum fluctuations represented by the light-front Fock expansion leads to novel QCD phenomena such as color transparency, intrinsic heavy quark distributions, diffractive dissociation, and hidden-color components of nuclear wavefunctions. A new test of hidden color in deuteron photodisintegration is proposed. The origin of leading-twist phenomena such as the diffractive component of deep inelastic scattering, single-spin asymmetries, nuclear shadowing and antishadowing is also discussed; these phenomena cannot be described by lightfront wavefunctions of the target computed in isolation. Part of the anomalous NuTeV results for the weak mixing angle θ W could be due to the non-universality of nuclear antishadowing for charged and neutral currents.2

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“…Before concluding let us add a few comments: and incident parton energy loss in nuclear matter has been discussed in [16,17,18]. In this approach the shadowing is understood as destructive interference derived from the space-time properties of nuclear interaction which is of a similar origin as the suppression considered in our model.…”

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confidence: 95%

An alternative model of jet suppression at RHIC energies

et al. 2003

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We propose a simple Glauber-type mechanism for suppression of jet production up to transverse momenta of about 10 GeV/c at RHIC. For processes in this kinematic region, the formation time is smaller than the interval between two successive hard partonic collisions and the subsequent collision influences the jet production. Number of jets then roughly scales with the number of participants. Proportionality to the number of binary collisions is recovered for very high transverse momenta. The model predicts suppression of jet production in d+Au collisions at RHIC.

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Statistical Physics and Light-Front Quantization

Cited by 3 publications

References 28 publications

Drell-Yan process in pA collisions: Path-integral treatment of coherence effects

Drell-Yan process in pA collisions: Path-integral treatment of coherence effects

Light-Front QCD

An alternative model of jet suppression at RHIC energies

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