7,966 research outputs found
Excitation of open charm and factorization breaking in rapidity gap events at HERA
We develop the pQCD description of diffraction excitation of heavy flavours
in DIS and we derive the analytic formulas for the mass spectrum in leading
log. The result illustrates nicely non-factorization properties of the
QCD pomeron. We predict a very steep rise of the charm content of diffraction
dissociation of photons at small x_{\Pom}. We evaluate the contribution of
open charm to scaling violations in the structure function of the pomeron.Comment: 13 pages. Accepted for publication on march 10th 1996 by Phys. Lett.
Factorization properties of the diffraction dissociation of longitudinal photons
We develop the pQCD description of the diffraction dissociation (DD) of
longitudinal photons. We demonstrate that the longitudinal diffractive
structure function does not factor into the flux of pomerons and the partonic
structure function of the pomeron, thus defying the usually assumed Regge
factorization. In contrast to DD of the transverse photons, DD of the
longitudinal photons is strongly peaked at . We comment on duality
properties of DD in deep inelastic scattering.Comment: 11 page
Diffraction in Charged Current DIS
We present the QCD calculation of the diffractive structure function for
charged current DIS. In particular we analyse the perturbatively tractable
excitation of heavy quarks. We emphasize the peculiarities of the Regge
factorization breaking in excitation of open charm.Comment: 16 pages LateX, 5 eps figures include
3D Jet Tomography of Twisted Strongly Coupled Quark Gluon Plasmas
The triangular enhancement of the rapidity distribution of hadrons produced
in p+A reactions relative to p+p is a leading order in A^{1/3}/log(s) violation
of longitudinal boost invariance at high energies. In A+A reactions this leads
to a trapezoidal enhancement of the local rapidity density of produced gluons.
The local rapidity gradient is proportional to the local participant number
asymmetry, and leads to an effective rotation in the reaction plane. We propose
that three dimensional jet tomography, correlating the long range rapidity and
azimuthal dependences of the nuclear modification factor,
R_{AA}(\eta,\phi,p_\perp; b>0), can be used to look for this intrinsic
longitudinal boost violating structure of collisions to image the
produced twisted strongly coupled quark gluon plasma (sQGP). In addition to
dipole and elliptic azimuthal moments of R_{AA}, a significant high p_\perp
octupole moment is predicted away from midrapidity. The azimuthal angles of
maximal opacity and hence minima of R_{AA} are rotated away from the normal to
the reaction plane by an `Octupole Twist' angle, \theta_3(\eta), at forward
rapidities.Comment: 10 Pages, 16 Figures, RevTex, Replaced with Peer reviewed verion for
PR
Evolution of high-mass diffraction from the light quark valence component of the pomeron
We analyze the contribution from excitation of the Fock states of the photon to high mass diffraction in
DIS. We show that the large behavior of this contribution can be
described by the DLLA evolution from the non-perturbative valence
state of the pomeron. Although of higher order in pQCD, the new contribution to
high-mass diffraction is comparable to that from the excitation of the Fock state of the photon.Comment: 12 pages, 2 figures, the oublished version. The slight numerical
errors corrected, all conclusions are retaine
The Running BFKL: Resolution of Caldwell's Puzzle
The HERA data on the proton structure function, , at very small
and show the dramatic departure of the logarithmic slope, , from theoretical predictions based on the DGLAP
evolution. We show that the running BFKL approach provides the quantitative
explanation for the observed and/or -dependence of .Comment: 7 pages, Latex, 4 Figures, P
Excitonic Mott transition in double quantum wells
We consider an electron-hole system in double quantum wells theoretically. We
demonstrate that there is a temperature interval over which an abrupt jump in
the value of the ionization degree occurs with an increase of the carrier
density or temperature. The opposite effect - the collapse of the ionized
electron-hole plasma into an insulating exciton system - should occur at lower
densities. In addition, we predict that under certain conditions there will be
a sharp decrease of the ionization degree with increasing temperature - the
anomalous Mott transition. We discuss how these effects could be observed
experimentally.Comment: 6 pages, 4 figure
Breaking of k_\perp-factorization for Single Jet Production off Nuclei
The linear k_\perp-factorization is part and parcel of the pQCD description
of high energy hard processes off free nucleons.
In the case of heavy nuclear targets the very concept of nuclear parton
density becomes ill-defined as exemplified by the recent derivation [2] of
nonlinear nuclear k_\perp-factorization for forward dijet production in DIS off
nuclei. Here we report a derivation of the related breaking of
k_\perp-factorization for single-jet processes. We present a general formalism
and apply it to several cases of practical interest: open charm and quark and
gluon jet production in the central to beam fragmentation region of
\gamma^*p,\gamma^*A, pp and pA collisions. We show how the pattern of
k_\perp-factorization breaking and the nature and number of exchanged nuclear
pomerons do change within the phase space of produced quark and gluon jets. As
an application of the nonlinear k_\perp-factorization we discuss the Cronin
effect. Our results are also applicable to the p_\perp-dependence of the
Landau-Pomeranchuk-Migdal effect for, and nuclear quenching of, jets produced
in the proton hemisphere of pA collisions.Comment: 55 pages, 9 eps figures, presentation shortened, a number of typos
removed, to appear in Phys. Rev.
First analytic correction beyond PFA for the electromagnetic field in sphere-plane geometry
We consider the vacuum energy for a configuration of a sphere in front of a
plane, both obeying conductor boundary condition, at small separation. For the
separation becoming small we derive the first next-to-leading order of the
asymptotic expansion in the separation-to-radius ratio \ep. This correction
is of order \ep. In opposite to the scalar cases it contains also
contributions proportional to logarithms in first and second order, \ep \ln
\ep and \ep (\ln \ep)^2. We compare this result with the available findings
of numerical and experimental approaches.Comment: 20 pages, 1 figur
- …