23,695 research outputs found
Higher-Twist Dynamics in Large Transverse Momentum Hadron Production
A scaling law analysis of the world data on inclusive large-pT hadron
production in hadronic collisions is carried out. A significant deviation from
leading-twist perturbative QCD predictions at next-to-leading order is
reported. The observed discrepancy is largest at high values of xT=2pT/sqrt(s).
In contrast, the production of prompt photons and jets exhibits the scaling
behavior which is close to the conformal limit, in agreement with the
leading-twist expectation. These results bring evidence for a non-negligible
contribution of higher-twist processes in large-pT hadron production in
hadronic collisions, where the hadron is produced directly in the hard
subprocess rather than by gluon or quark jet fragmentation. Predictions for
scaling exponents at RHIC and LHC are given, and it is suggested to trigger the
isolated large-pT hadron production to enhance higher-twist processes.Comment: 5 pages, 4 figures. Extended introduction, additional reference
Stability of the U(1) spin liquid with spinon Fermi surface in 2+1 dimensions
We study the stability of the 2+1 dimensional U(1) spin liquid state against
proliferation of instantons in the presence of spinon Fermi surface. By mapping
the spinon Fermi surface into an infinite set of 1+1 dimensional chiral
fermions, it is argued that an instanton has an infinite scaling dimension for
any nonzero number of spinon flavors. Therefore, the spin liquid phase is
stable against instantons and the non-compact U(1) gauge theory is a good low
energy description.Comment: 14 pages, 7 figures, v3) minor corrections, to appear in PR
X-ray Raman compression via two-stream instability in dense plasmas
A Raman compression scheme suitable for x-rays, where the Langmuir wave is
created by an intense beam rather than the pondermotive potential between the
seed and pump pulses, is proposed.
The required intensity of the seed and pump pulses enabling the compression
could be mitigated by more than a factor of 100, compared to conventionally
available other Raman compression schemes. The relevant wavelength of x-rays
ranges from 1 to 10 nm
Low energy effective theory of Fermi surface coupled with U(1) gauge field in 2+1 dimensions
We study the low energy effective theory for a non-Fermi liquid state in 2+1
dimensions, where a transverse U(1) gauge field is coupled with a patch of
Fermi surface with N flavors of fermion in the large N limit. In the low energy
limit, quantum corrections are classified according to the genus of the 2d
surface on which Feynman diagrams can be drawn without a crossing in a double
line representation, and all planar diagrams are important in the leading
order. The emerging theory has the similar structure to the four dimensional
SU(N) gauge theory in the large N limit. Because of strong quantum fluctuations
caused by the abundant low energy excitations near the Fermi surface, low
energy fermions remain strongly coupled even in the large N limit. As a result,
there are infinitely many quantum corrections that contribute to the leading
frequency dependence of the Green's function of fermion on the Fermi surface.
On the contrary, the boson self energy is not modified beyond the one-loop
level and the theory is stable in the large N limit. The non-perturbative
nature of the theory also shows up in correlation functions of gauge invariant
operators.Comment: 14 pages, 20 figures; v2) Sec. V on correlation function of gauge
invariant operators added; v3) typos corrected, minor changes (to appear in
PRB
Higher-twist contributions to large pT hadron production in hadronic collisions
The scaling behavior of large-pT hadron production in hadronic collisions is
investigated. A significant deviation from the NLO QCD predictions is reported,
especially at high values of xT=2pT/sqrt(s). In contrast, the prompt photon and
jet production data prove in agreement with leading-twist expectations. These
results are interpreted as coming from a non-negligible contribution of
higher-twist processes, where the hadron is produced directly in the hard
subprocess. Predictions for scaling exponents at RHIC are successfully compared
to PHENIX preliminary measurements. We suggest to trigger on isolated large-pT
hadron production to enhance higher-twist processes, and point that the use of
isolated hadrons as a signal for new physics at colliders can be affected by
the presence of direct hadron production processes.Comment: 4 pages, 2 figures. Talk given at the 45th Rencontres de Moriond QCD
and High Energy Interactions, La Thuile, Italy, 13-20 March 201
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