314 research outputs found
Final state hadronic interactions and non-resonant decays
We evaluate the non-resonant decay amplitude of the process using an approach based on final state hadronic interactions
described in terms of meson exchanges. We conclude that this mechanism
generates inhomogeneities in the Dalitz plot of the B decay.Comment: 6 pages, 5 figures. Major changes. Version accepted for publication
in Phys. Lett.
Analysis of the Y(4140) and related molecular states with QCD sum rules
In this article, we assume that there exist scalar , , and
molecular states, and study their masses using
the QCD sum rules. The numerical results indicate that the masses are about
above the corresponding ,
, and thresholds, the Y(4140) is unlikely a scalar molecular state. The scalar ,
, and molecular states maybe not exist, while the scalar , , and
molecular states maybe exist.Comment: 19 pages, 36 figures, slight revisio
Symmetry Nonrestoration in a Gross-Neveu Model with Random Chemical Potential
We study the symmetry behavior of the Gross-Neveu model in three and two
dimensions with random chemical potential. This is equivalent to a four-fermion
model with charge conjugation symmetry as well as Z_2 chiral symmetry. At high
temperature the Z_2 chiral symmetry is always restored. In three dimensions the
initially broken charge conjugation symmetry is not restored at high
temperature, irrespective of the value of the disorder strength. In two
dimensions and at zero temperature the charge conjugation symmetry undergoes a
quantum phase transition from a symmetric state (for weak disorder) to a broken
state (for strong disorder) as the disorder strength is varied. For any given
value of disorder strength, the high-temperature behavior of the charge
conjugation symmetry is the same as its zero-temperature behavior. Therefore,
in two dimensions and for strong disorder strength the charge conjugation
symmetry is not restored at high temperature.Comment: 16 pages, 3 figure
Modelling of strain effects in manganite films
Thickness dependence and strain effects in films of
perovskites are analyzed in the colossal magnetoresistance regime. The
calculations are based on a generalization of a variational approach previously
proposed for the study of manganite bulk. It is found that a reduction in the
thickness of the film causes a decrease of critical temperature and
magnetization, and an increase of resistivity at low temperatures. The strain
is introduced through the modifications of in-plane and out-of-plane electron
hopping amplitudes due to substrate-induced distortions of the film unit cell.
The strain effects on the transition temperature and transport properties are
in good agreement with experimental data only if the dependence of the hopping
matrix elements on the bond angle is properly taken into account.
Finally variations of the electron-phonon coupling linked to the presence of
strain turn out important in influencing the balance of coexisting phases in
the filmComment: 7 figures. To be published on Physical Review
Weak Segregation Theory and Non-Conventional Morphologies in the Ternary ABC Triblock Copolymers
The Leibler weak segregation theory in molten diblock copolymers is
generalized with due regard for the 2nd shell harmonics contributions defined
in the paper and the phase diagrams are built for the linear and miktoarm
ternary ABC triblock copolymers. The symmetric linear copolymers with the
middle block non-selective with respect to the side ones are shown to undergo
the continuous ODT not only into the lamellar phase but also into various
non-conventional cubic phases (depending on the middle block composition it
could be the simple cubic, face-centered cubic or non-centrosymmetric phase
revealing the symmetry of space group No.214 first predicted to appear in
molten block copolymers). For asymmetric linear ABC copolymers a region of
compositions is found where the weakly segregated gyroid (double gyroid) phase
exists between the planar hexagonal and lamellar or one of the non-conventional
cubic phases up to the very critical point. In contrast, the miktoarm ABC block
copolymers with one of its arm non-selective with respect to the two others are
shown to reveal a pronounced tendency towards strong segregation, which is
preceded by increase of stability of the conventional BCC phase and a peculiar
weakly segregated BCC phase (BCC3), where the dominant harmonics belong to the
3rd co-ordination sphere of the reciprocal lattice. The validity region of the
developed theory is discussed and outlined in the composition triangles both
for linear and miktoarm copolymers.Comment: 61 pages, 12 figure
K^* Mesons and Nucleon Strangeness
We study contributions to the nucleon strange quark vector current form
factors from intermediate states containing K^* mesons. We show how these
contributions may be comparable in magnitude to those made by K mesons, using
methods complementary to those employed in quark model studies. We also analyze
the degree of theoretical uncertainty associated with K^* contributions.Comment: 21 pages, RevTex, 2 PS figures included with epsf.st
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in âs = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fbâ1 of protonâproton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
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