2,460 research outputs found
Bottomonia Hadroproduction
We analyze Tevatron data of bottomonium hadroproduction in the framework of
the colour-octet model (COM) implemented in the event generator PYTHIA using
CTEQ4L PDF taking into account initial-state radiation of gluons and
Altarelli-Parisi evolution of final-state gluons. We obtain new values for the
colour-octet matrix elements relevant to this production process for the
Upsilon(nS) family (n=1,2,3), finding that the ^1S_0^{(8)}+^3P_J^{(8)}
contributions are not needed in the fit. We show the different contributions to
Upsilon(1S) production at Tevatron for p_T>8 GeV, comparing them with CDF data.
Finally we extrapolate to LHC energies to predict Upsilon(nS) production rates.Comment: Talk given at 4th International Conference on Hyperons, Charm and
Beauty Hadrons, Valencia, Spain, 27-30 Jun 2000. LaTeX, 4 pages, 4 EPS
figure
J/psi Production at the LHC
We firstly examine hadroproduction of prompt J/psi's at the Fermilab Tevatron
in a Monte Carlo Framework by means of the event generator PYTHIA 5.7 in which
those colour-octet matrix elements processes relevant for charmonium production
have been implemented accordingly. We find that colour-octet matrix elements
presented in literature from p-pbar collider data are systematically
overestimated due to overlooking of the effective primordial transverse
momentum of partons (i.e. including higher-order QCD effects). We estimate the
size of these effects using different parton distribution functions. Finally,
after normalization to Tevatron data, we extrapolate up to LHC energies making
a prediction on the expected pt differential cross-section for charmonium.Comment: 4 pages, LaTex, 3 Figures included in the text, Contribution to the
2nd Int. Conference on Hyperons, charm and beauty hadrons (Montreal, Aug
27-30, 1996
Domain Bubbles of Extra Dimensions
``Dimension bubbles'' of the type previously studied by Blau and Guendelman
[S.K. Blau and E.I. Guendelman, Phys. Rev. D40, 1909 (1989)], which effectively
enclose a region of 5d spacetime and are surrounded by a region of 4d
spacetime, can arise in a 5d theory with a compact extra dimension that is
dimensionally reduced to give an effective 4d theory. These bubbles with thin
domain walls can be stabilized against total collapse in a rather natural way
by a scalar field which, as in the case with ``ordinary'' nontopological
solitons, traps light scalar particles inside the bubble.Comment: 13 pages, no figures; to appear in Phys.Rev.
Bottomonium Production at the Tevatron and the LHC
Inclusive bottomonium hadroproduction at the Tevatron is firstly examined in
a Monte Carlo framework with the colour-octet mechanism implemented in the
event generation. We extract some NRQCD colour-octet matrix elements relevant
for hadroproduction. Remarkably we find a quite small
contribution (compatible with zero) from feeddown of states
produced through the colour-octet mechanism: indirect production
via decays should be mainly ascribed to the colour-singlet model.
Finally we extrapolate to LHC energies to predict prompt
production rates.Comment: LaTeX, 11 pages, 6 EPS figure
Aharonov-Bohm Effect on Noncommutative Plane: A Coherent State Approach
We apply the coherent state approach to study Aharonov-Bohm effect in the
field theory context. We verify that, contrarily to the commutative result, the
scattering amplitude is ultraviolet finite. However, we have logarithmic
singularities as the noncommutative parameter tends to zero. Thus, the
inclusion of a quartic self-interaction for the scalar field is necessary to
obtain a smooth commutative limit.Comment: 14 pages, 4 figures, minor correction
Electromagnetic Decays of Heavy Baryons
The electromagnetic decays of the ground state baryon multiplets with one
heavy quark are calculated using Heavy Hadron Chiral Perturbation Theory. The
M1 and E2 amplitudes for S^{*}--> S gamma, S^{*} --> T gamma and S --> T gamma
are separately computed. All M1 transitions are calculated up to
O(1/Lambda_chi^2). The E2 amplitudes contribute at the same order for S^{*}-->
S gamma, while for S^{*} --> T gamma they first appear at O(1/(m_Q
\Lambda_\chi^2)) and for S --> T gamma are completely negligible. The
renormalization of the chiral loops is discussed and relations among different
decay amplitudes are derived. We find that chiral loops involving
electromagnetic interactions of the light pseudoscalar mesons provide a sizable
enhancement of these decay widths. Furthermore, we obtain an absolute
prediction for the widths of Xi^{0'(*)}_c--> Xi^{0}_c gamma and Xi^{-'(*)}_b-->
Xi^{-}_b gamma. Our results are compared to other estimates existing in the
literature.Comment: 17 pages, 3 figures, submitted to Phys. Rev.
Efficient scheme for one-way quantum computing in thermal cavities
We propose a practical scheme for one-way quantum computing based on
efficient generation of 2D cluster state in thermal cavities. We achieve a
controlled-phase gate that is neither sensitive to cavity decay nor to thermal
field by adding a strong classical field to the two-level atoms. We show that a
2D cluster state can be generated directly by making every two atoms collide in
an array of cavities, with numerically calculated parameters and appropriate
operation sequence that can be easily achieved in practical Cavity QED
experiments. Based on a generated cluster state in Box configuration,
we then implement Grover's search algorithm for four database elements in a
very simple way as an example of one-way quantum computing.Comment: 6 pages, 3 figure
Chiral Multiplets of Heavy-Light Mesons
The recent discovery of a narrow resonance in D_s+pi^0 by the BABAR
collaboration is consistent with the interpretation of a heavy J^P(0+,1+) spin
multiplet. This system is the parity partner of the groundstate (0-,1-)
multiplet, which we argue is required in the implementation of SU(3)_L x
SU(3)_R chiral symmetry in heavy-light meson systems. The (0+,1+)->(0-,1-)+pi
transition couplings satisfy a Goldberger-Treiman relation, g_pi =
Delta(M)/f_pi, where Delta(M) is the mass gap. The BABAR resonance fits the 0+
state, with a kinematically blocked principal decay mode to D+K. The allowed
D_s+pi, D_s+2pi and electromagnetic transitions are computed from the full
chiral theory and found to be suppressed, consistent with the narrowness of the
state. This state establishes the chiral mass difference for all such
heavy-quark chiral multiplets, and precise predictions exist for the analogous
B_s and strange doubly-heavy baryon states.Comment: 10 pages; minor editorial revisions; recomputed M1 transitio
symmetry, electroweak transition, and magnetic monopoles at high temperature
We consider the lattice realization of the Standard Model with an additional
symmetry. Numerical simulations were performed on the asymmetric lattice,
which corresponds to the finite temperature theory. Our choice of parameters
corresponds to large Higgs masses ( Gev). The phase diagram was
investigated and has been found to be different from that of the usual lattice
realization of the Standard Model. It has been found, that the
confinement-deconfinement phase transition lines for the SU(2) and SU(3) fields
coincide. The transition line between Higgs and symmetric deconfinement parts
of the phase diagram and the confinement-deconfinement transition line meet in
a triple point. The transition between Higgs and symmetric parts of the phase
diagram corresponds to the finite temperature electroweak transition/crossover.
We see for the first time evidence that Nambu monopoles are condensed at
while at their condensate vanishes.Comment: Latex, 14 page
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