231 research outputs found
Regge-cascade hadronization
We argue that the evolution of coloured partons into colour-singlet hadrons
has approximate factorization into an extended parton-shower phase and a
colour-singlet resonance--pole phase. The amplitude for the conversion of
colour connected partons into hadrons necessarily resembles Regge-pole
amplitudes since qq-bar resonance amplitudes and Regge-pole amplitudes are
related by duality. A `Regge-cascade' factorization property of the N-point
Veneziano amplitude provides further justification of this protocol. This
latter factorization property, in turn, allows the construction of general
multi-hadron amplitudes in amplitude-squared factorized form from (1->2) link
amplitudes. We suggest an algorithm with cascade-decay configuration, ordered
in the transverse momentum, suitable for Monte-Carlo simulation. We make a
simple implementation of this procedure in Herwig++, obtaining some improvement
to the description of the event-shape distributions at LEP.Comment: 10 pages, 9 figure
Low energy neutrino scattering measurements at future Spallation Source facilities
In the future several Spallation Source facilities will be available
worldwide. Spallation Sources produce large amount of neutrinos from
decay-at-rest muons and thus can be well adapted to accommodate
state-of-the-art neutrino experiments. In this paper low energy neutrino
scattering experiments that can be performed at such facilities are reviewed.
Estimation of expected event rates are given for several nuclei, electrons and
protons at a detector located close to the source. A neutrino program at
Spallation Sources comprises neutrino-nucleus cross section measurements
relevant for neutrino and core-collapse supernova physics, electroweak tests
and lepton-flavor violation searches.Comment: 12 pages, 4 figures, 5 table
Monte Carlo simulation for jet fragmentation in SUSY-QCD
We present results from a new Monte Carlo simulation for jet fragmentation in
QCD and SUSY QCD for large primary energies up to GeV. In
the case of SUSY QCD the simulation takes into account not only gluons and
quarks as cascading particles, but also their supersymmetric partners. A new
model-independent hadronization scheme is developed, in which the hadronization
functions are found from LEP data. An interesting feature of SUSY QCD is the
prediction of a sizeable flux of the lightest supersymmetric particles (LSPs),
if R-parity is conserved. About 10% of the jet energy is transferred to LSPs
which, owing to their harder spectra, constitute an important part of the
spectra for large . Spectra of protons and of secondary particles,
photons and neutrinos, are also calculated. These results have implications for
the decay of superheavy particles with masses up to the GUT scale, which have
been suggested as a source of ultrahigh energy cosmic rays.Comment: latex, 25 pages with 17 eps figure
Present status of the nonstrange and other flavor partners of the exotic Theta+ baryon
Given the existing empirical information about the exotic Theta+ baryon, we
analyze possible properties of its SU(3)F-partners, paying special attention to
the nonstrange member of the antidecuplet N*. The modified piN partial-wave
analysis presents two candidate masses, 1680 MeV and 1730 MeV. In both cases,
the N* should be rather narrow and highly inelastic. Our results suggest
several directions for experimental studies that may clarify properties of the
antidecuplet baryons, and structure of their mixing with other baryons. Recent
experimental evidence from the GRAAL and STAR Collaborations could be
interpreted as observations of a candidate for the Theta+ nonstrange partner.Comment: 4 pages, 1 figure, talk given at the Topical Group on Hadron Physics
(Fermilab, Oct. 24-26, 2004
Corrections to Angular Ordering in Multiple Hadroprodroproduction
One of the key ideas in describing the multiparticle production at high
energies in the perturbative QCD is the angular ordering in successive
soft-gluon emission. We analyse the angular distribution of particles in a jet,
and investigate the corrections to the angular ordering. At a small angle from
the jet direction, the angular ordering is exact at the next-to-leading order.
At a large angle, the angular ordering overestimates the angular particle
density by a factor , where is the
anomalous dimension of the multiplicity. The correction restores
the boost invariance of the cross section.Comment: Latex fil
Resonances, and mechanisms of Theta-production
After explaining necessity of exotic hadrons, we discuss mechanisms which
could determine production of the exotic Theta-baryon. A possible important
role of resonances (producing the Theta in real or virtual decays) is
emphasized for various processes. Several experimental directions for studies
of such resonances, and the Theta itself, are suggested. We briefly discuss
also recent negative results on the Theta-baryon.Comment: 6 page
Grand Unification Signal from Ultra High Energy Cosmic Rays?
The spectrum of ultrahigh energy (above \approx 10^{9} GeV) cosmic rays is
consistent with the decay of GUT scale particles. The predicted mass is
m_X=10^b GeV, where b=14.6_{-1.7}^{+1.6}.Comment: 4 pages, 3 figures one figure removed, one table added, conclusions
essentially remained the same within errorbar
Two-particle rapidity correlations between relativistic particles in central collisions of 197 Au nuclei in emulsion at 11.6 A GeV/c
Evolution of average multiplicities of quark and gluon jets
The energy evolution of average multiplicities of quark and gluon jets is
studied in perturbative QCD. Higher order (3NLO) terms in the perturbative
expansion of equations for the generating functions are found. First and second
derivatives of average multiplicities are calculated. The mean multiplicity of
gluon jets is larger than that of quark jets and evolves more rapidly with
energy. It is shown which quantities are most sensitive to higher order
perturbative and nonperturbative corrections. We define the energy regions
where the corrections to different quantities are important. The latest
experimental data are discussed.Comment: 23 pages including 3 figures. Version 2 contains small correction to
equation (41
Multiplicity distributions in a thermodynamical model of hadron production in collisions
Predictions of a thermodynamical model of hadron production for multiplicity
distributions in annihilations at LEP and PEP-PETRA centre of mass
energies are shown. The production process is described as a two-step process
in which primary hadrons emitted from the thermal source decay into final
observable particles. The final charged tracks multiplicity distributions turn
out to be of Negative Binomial type and are in quite good agreement with
experimental observations. The average number of clans calculated from fitted
Negative Binomial coincides with the average number of primary hadrons
predicted by the thermodynamical model, suggesting that clans should be
identified with primary hadrons.Comment: 15 pages, LaTeX file, uses epsfig.sty and cite.sty, 3 figures added
as uu-encoded g-zipped tarred eps-file
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