119389477
Mixed quark-gluon condensate from instantons
Abstract We calculate the vacuum expectation value of the dimension-5 “mixed” quark-gluon operator, O σ = Ψ 1 2 λ a σ μν ΨF μν a , in the instanton vacuum. Within the 1 N c -expansion the QCD operator is replaced by an effective many-fermion operator, which is averaged over the effetive theory of massive quarks derived from instantons. We find m 0 2 ≡ 〈O σ 〉/〈 Ψ Ψ〉 ≈ 4 ϱ – = 1.4 GeV 2 , somewhat larger than the estimate from QCD sum rules for the nucleon.
16303633
Rapidity gap survival in central exclusive diffraction: Dynamical mechanisms and uncertainties
We summarize our understanding of the dynamical mechanisms governing rapidity gap survival in central exclusive diffraction, pp -> p + H + p (H = high-mass system), and discuss the uncertainties in present estimates of the survival probability. The main suppression of diffractive scattering is due to inelastic soft spectator interactions at small pp impact parameters and can be described in a mean-field approximation (independent hard and soft interactions). Moderate extra suppression results from fluctuations of the partonic configurations of the colliding protons. At LHC energies absorptive interactions of hard spectator partons associated with the gg -> H process reach the black-disk regime and cause substantial additional suppression, pushing the survival probability below 0.01.
125666710
Nucleon matrix elements of twist - three and twist -4 operators from the instanton vacuum
119292449
Nuclear physics with a medium-energy Electron-Ion Collider
A polarized ep/eA collider (Electron-Ion Collider, or EIC) with variable center-of-mass energy √s ∼ 20–70 GeV and luminosity ∼1034 cm−2 s−1 would be uniquely suited to address several outstanding questions of Quantum Chromodynamics (QCD) and the microscopic structure of hadrons and nuclei: i) the three-dimensional structure of the nucleon in QCD (sea quark and gluon spatial distributions, orbital motion, polarization, correlations); ii) the fundamental color fields in nuclei (nuclear parton densities, shadowing, coherence effects, color transparency); iii) the conversion of color charge to hadrons (fragmentation, parton propagation through matter, in-medium jets). We briefly review the conceptual aspects of these questions and the measurements that would address them, emphasizing the qualitatively new information that could be obtained with the collider. Such a medium-energy EIC could be realized at Jefferson Lab after the 12GeV Upgrade (MEIC), or at Brookhaven National Lab as the low-energy stage of eRHIC.
16801030
Polarized antiquark flavor asymmetry in Drell–Yan pair production
Abstract. We investigate the role of the flavor asymmetry of the nucleon's polarized antiquark distributions in Drell–Yan lepton pair production in polarized nucleon–nucleon collisions at HERA (fixed–target) and RHIC energies. It is shown that the large polarized antiquark flavor asymmetry predicted by model calculations in the large–$N_c$ limit (chiral quark–soliton model) has a dramatic effect on the double spin asymmetries in high mass lepton pair production, as well as on the single spin asymmetries in lepton pair production through $W^\pm$–bosons at $M^2 = M_W^2$.
55072904
Transverse nucleon structure and diagnostics of hard parton-parton processes at LHC
We propose a new method to determine at what transverse momenta particle production in high-energy pp collisions is governed by hard parton-parton processes. Using information on the transverse spatial distribution of partons obtained from hard exclusive processes in ep/\gamma p scattering, we evaluate the impact parameter distribution of pp collisions with a hard parton-parton process as a function of p_T of the produced parton (jet). We find that the average pp impact parameters in such events depend very weakly on p_T in the range 2 < p_T < few 100 GeV, while they are much smaller than those in minimum-bias inelastic collisions. The impact parameters in turn govern the observable transverse multiplicity in such events (in the direction perpendicular to the trigger particle or jet). Measuring the transverse multiplicity as a function of p_T thus provides an effective tool for determining the minimum p_T for which a given trigger particle originates from a hard parton-parton process.
22188300
Differences between mean-field dynamics and N-particle quantum dynamics as a signature of entanglement.
A Bose-Einstein condensate in a tilted double-well potential under the influence of time-periodic potential differences is investigated in the regime where the mean-field (Gross-Pitaevskii) dynamics become chaotic. For some parameters near stable regions, even averaging over several condensate oscillations does not remove the differences between mean-field and N-particle results. While introducing decoherence via piecewise deterministic processes reduces those differences, they are due to the emergence of mesoscopic entangled states in the chaotic regime.
27937897
Creation and detection of a mesoscopic gas in a nonlocal quantum superposition.
We investigate the scattering of a quantum matter wave soliton on a barrier in a one-dimensional geometry, and we show that it can lead to mesoscopic quantum superposition states, where the atomic gas is in a coherent superposition of being in the half-space to the left of the barrier and being in the half-space to the right of the barrier. We propose an interferometric method to reveal the coherent nature of this superposition, and we discuss in detail the experimental feasibility.