15375029
SMALL-x PHYSICS: From HERA to LHC and Beyond
▪ Abstract We summarize the lessons learned from studies of hard scattering processes in high-energy electron-proton collisions at HERA and antiproton-proton collisions at the Tevatron, with the ai...
120126390
Chiral symmetry restoration and the skyrme model
Abstract Applications of the Skyrme model to dense baryonic matter reveal a transition from a low-density phase of localized skyrmions to a high-density phase possessing an additional half-skyrmion symmetry. We suggest that this transition should be regarded as the restoration of chiral symmetry at high densities. This is based on (i) the vanishing of the matrix element for pion decay and (ii) the appearance of parity doublets in both the strange and non-strange sectors at high density and (iii) the appearance of a triplet of massless “Goldstone bosons” at low density.
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.
15745876
Estimates of higher-dimensional vacuum condensates from the instanton vacuum
We calculate the values of non-factorizable dimension-7 vacuum condensates in the instanton vacuum. We comment on a method, recently proposed by Oganesian, to estimate the dimension-7 condensates by factorization of dimension-10 condensates in various inequivalent ways. The instanton estimates could be used to analyze the stability of QCD sum rules with increasing dimensions.
125666710
Nucleon matrix elements of twist - three and twist -4 operators from the instanton vacuum
17230719
Chiral Lagrangian for excited pions
We construct a chiral Lagrangian containing, in addition to the usual pion field ({pi}), also its first radial excitation ({pi}{sup {prime}}). The Lagrangian is derived in the large-N{sub c} limit from a Nambu{endash}Jona-Lasinio (NJL) quark model with separable nonlocal interactions, with form factors corresponding to three-dimensional ground- and excited-state wave functions. Chiral symmetry breaking is governed by the NJL gap equation. The effective Lagrangian for {pi} and {pi}{sup {prime}} mesons shows the decoupling of the Goldstone pion and the vanishing of the {pi}{sup {prime}} leptonic decay constant f{sub {pi}{sup {prime}}} in the chiral limit, as required by axial-vector current conservation. We derive the excited-state contribution to the axial-vector current of the model using Noether{close_quote}s theorem. For a finite pion mass and {pi}{sup {prime}} masses in the range of 750{endash}1300 MeV, f{sub {pi}{sup {prime}}}/f{sub {pi}} is found to be of the order of 1{percent}. {copyright} {ital 1997} {ital The American Physical Society}
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.