15,315,068 research outputs found
Astronomical spectrograph calibration with broad-spectrum frequency combs
Broadband femtosecond-laser frequency combs are filtered to
spectrographically resolvable frequency-mode spacing, and the limitations of
using cavities for spectral filtering are considered. Data and theory are used
to show implications to spectrographic calibration of high-resolution,
astronomical spectrometers
Inclusive omega photoproduction off nuclei
We investigate inclusive omega photoproduction off complex nuclei,
concentrating on the feasibility to examine a possible in-medium change of the
omega meson properties by observing the pi^0 gamma invariant mass spectrum. The
simulations are performed by means of a BUU transport model including a full
coupled-channel treatment of the final state interactions. In-medium changes of
the omega spectral density are found to yield a moderate modification of the
observables as compared to the situation in free space. Also the effects of a
momentum dependence of the strong omega potential are discussed.Comment: 19 pages, 12 figures, minor corrections, accepted for publication in
EPJ
Reconclining phi radiative decays with other data for a0(980), fo(980), pi-pi -> KK and pi-pi -> eta-eta
Data for phi -> gamma (eta-pizero) are analysed using the KK loop model and
compared with parameters of a0(980) derived from Crystal Barrel data. The
eta-pi mass spectrum agrees closely and the absolute normalisation lies just
within errors. However, BES parameters for fo(980) predict a normalisation for
phi -> gamma (pizero-pizero) at least a factor 2 lower than is observed. This
discrepancy may be eliminated by including constructive interference between
fo(980) and sigma. The magnitude required for sigma -> KK is consistent with
data on pi-pi -> KK. A dispersion relation analysis by Buttiker, Descotes-Genon
and Moussallam of pi-pi -> KK leads to a similar conclusion. Data on pi-pi ->
eta-eta also require decays of sigma to eta-eta. Four sets of pi-pi -> KK data
all require a small but definite fo(1370) signal.Comment: 21 pages, 11 figures, Small rearrangement of reference
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
Coherent Production of Pairs of Parabosons of Order 2
A parameter-free statistical model is used to study multiplicity signatures
for coherent production of charged-pairs of parabosons of order p=2 in
comparison with those arising in the case of ordinary bosons, p=1. Two
non-negative real parameters arise because "ab" and "ba" are fundamentally
distinct pair operators of charge "+1", A-quanta and charge "-1", B-quanta
parabosons. In 3D plots of P(q)_m = "The probability of m paraboson
charged-pairs and q positive parabosons" versus and , the p=1
curve is found to lie on the relatively narrow 2D p=2 surface.Comment: 25 pages, 16 figures, no macro
Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at TeV
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb
collisions at = 2.76 TeV have been measured by the ALICE
Collaboration at the LHC. The data are presented for central and peripheral
collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross
section. The measured charged particle spectra in and GeV/ are compared to the expectation in pp collisions at the same
, scaled by the number of underlying nucleon-nucleon
collisions. The comparison is expressed in terms of the nuclear modification
factor . The result indicates only weak medium effects ( 0.7) in peripheral collisions. In central collisions,
reaches a minimum of about 0.14 at -7GeV/ and increases
significantly at larger . The measured suppression of high- particles is stronger than that observed at lower collision energies,
indicating that a very dense medium is formed in central Pb-Pb collisions at
the LHC.Comment: 15 pages, 5 captioned figures, 3 tables, authors from page 10,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/98
B decays into light scalar particles and glueball
The recent observations of f_0(980) in charmless B-decays motivate further
studies of scalar particle and glueball production in these processes.
Amplitudes for charmless 2-body B decays involving the members of the scalar
nonet are presented based on the symmetries of the dominant penguin
contribution. Different scenarios for the lightest scalar nonet are
investigated in view of the presently available data. We describe the evidence
from B-decays for f_0(1500) with a flavour octet like mixing and the hints
towards the members of the q qbar nonet of lowest mass. There is further
support for the hypothesis of a broad 0^{++} glueball acting as coherent
background especially in B -> K Kbar K. The estimated B decay rates into
gluonic mesons represent a sizable fraction of the theoretically derived decay
rate for b -> sg.Comment: 34 pages, 5 figures, 8 tables, version to appear in Eur.Phys.J.C.,
with some clarifications in the text, additional refs. and several overall
signs in Tab.2,3 adde
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