97 research outputs found
Bose-Einstein Correlations for Systems with Large Halo
Model-independent considerations are presented for the calculation of
Bose-Einstein correlation functions and momentum distributions which describe
boson-emitting systems containing a central part surrounded by a large halo. If
the characteristic geometrical size of the halo is sufficiently large, the
contributions of central part and the halo to the invariant momentum
distribution are shown to be separable. The momentum-dependence of the
intercept parameter of the correlation function plays a central role. Almost
all high energy reactions including lepton-lepton, lepton hadron, hadron-hadron
and nuclear reactions are shown to be interpretable as boson emitting systems
with large halo. The results are applied to certain high energy heavy ion data
at CERN SPS. New insights are obtained for the description of low transverse
momentum enhancement of pions.Comment: Z. Phys. C in press, LaTeX, ReVTeX, 20 pages + 2 ps figure
Bounds for Bose-Einstein Correlation Functions
Bounds for the correlation functions of identical bosons are discussed for
the general case of a Gaussian density matrix. In particular, for a purely
chaotic system the two-particle correlation function must always be greater
than one. On the other hand, in the presence of a coherent component the
correlation function may take values below unity. The experimental situation is
briefly discussed.Comment: 7 pages, LaTeX, DMR-THEP-93-5/
Radiative rare decays revisited
We reexamine contributions of higher -resonances to the radiative rare
decays b\rar s\gamma in the limit where both - and -quark are
considered heavy. Using the non-relativistic quark model, and the form factor
definitions consistent with the HQET covariant trace formalism, we find
significant disagreement with previous work which also used heavy quark
symmetry, and excellent agreement with experimental results. In particular, the
two largest fractions of the inclusive b\rar s\gamma branching ratio are
found to be for B\rar K^{*}(892)\gamma and
for B\rar K_{2}^{*}(1430)\gamma decays. We also compare the contribution from
the radiative decays into the eight -meson states to the inclusive
experimental b\rar s\gamma mass distribution.Comment: Latex (uses epsf macro), 20 pages of text, 1 postscript figure
include
Bose-Einstein Correlations of Neutral and Charged Pions in Hadronic Z Decays
Bose-Einstein correlations of both neutral and like-sign charged pion pairs
are measured in a sample of 2 million hadronic Z decays collected with the L3
detector at LEP. The analysis is performed in the four-momentum difference
range 300 MeV < Q < 2 GeV. The radius of the neutral pion source is found to be
smaller than that of charged pions. This result is in qualitative agreement
with the string fragmentation model
Towards resolution of the enigmas of P-wave meson spectroscopy
The mass spectrum of P-wave mesons is considered in a nonrelativistic
constituent quark model. The results show the common mass degeneracy of the
isovector and isodoublet states of the scalar and tensor meson nonets, and do
not exclude the possibility of a similar degeneracy of the same states of the
axial-vector and pseudovector nonets. Current experimental hadronic and \tau
-decay data suggest, however, a different scenario leading to the a_1 meson
mass \simeq 1190 MeV and the K_{1A}-K_{1B} mixing angle \simeq (37\pm 3)^o.
Possible s\bar{s} states of the four nonets are also discussed.Comment: 22 pages, LaTe
The âmosaic habitatâ concept in human evolution: past and present
The habitats preferred by hominins and other species are an important theme in palaeoanthropology, and the âmosaic habitatâ (also referred to as habitat heterogeneity) has been a central concept in this regard for the last four decades. Here we explore the development of this concept â loosely defined as a range of different habitat types, such as woodlands, riverine forest and savannah within a limited spatial areaâ in studies of human evolution in the last sixty years or so. We outline the key developments that took place before and around the time when the term âmosaicâ came to wider palaeoanthropological attention. To achieve this we used an analysis of the published literature, a study of illustrations of hominin evolution from 1925 onwards and an email survey of senior researchers in palaeoanthropology and related fields. We found that the term mosaic starts to be applied in palaeoanthropological thinking during the 1970âs due to the work of a number of researchers, including Karl Butzer and Glynn Isaac , with the earliest usage we have found of âmosaicâ in specific reference to hominin habitats being by Adriaan Kortlandt (1972). While we observe a steady increase in the numbers of publications reporting mosaic palaeohabitats, in keeping with the growing interest and specialisation in various methods of palaeoenvironmental reconstruction, we also note that there is a lack of critical studies that define this habitat, or examine the temporal and spatial scales associated with it. The general consensus within the field is that the concept now requires more detailed definition and study to evaluate its role in human evolution
CP Violation in
We consider CP violating effects in the decays where both the resonance, , and
resonance, , can contribute. The interference
between the and resonances can lead to enhanced CP-violating
asymmetries whose magnitudes depend crucially on the decay
constant, . We make an estimate of with a
simplified chiral Lagrangian coupled to a massive pseudoscalar field, and we
compare the estimates from the non-relativistic quark model and from the QCD
sum rule with the estimate from the `mock' meson model. We then estimate
quantitatively the size of CP-violating effects in a multi-Higgs-doublet model
and scalar-leptoquark models. We find that, while CP-violating effects in the
scalar-leptoquark models may require more than leptons,
CP-violating effects from the multi-Higgs-doublet model can be seen at the
level with about leptons using the chiral Lagrangian
estimate of GeV.Comment: Latex, 30 pages, 2 figures (not included). Three compressed
postscript files of the paper available at
ftp://ftp.kek.jp/kek/preprints/TH/TH-419/kekth419.ps.gz, Tau1.ps.gz,
Tau2.ps.g
The Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a second generation water Cherenkov
detector designed to determine whether the currently observed solar neutrino
deficit is a result of neutrino oscillations. The detector is unique in its use
of D2O as a detection medium, permitting it to make a solar model-independent
test of the neutrino oscillation hypothesis by comparison of the charged- and
neutral-current interaction rates. In this paper the physical properties,
construction, and preliminary operation of the Sudbury Neutrino Observatory are
described. Data and predicted operating parameters are provided whenever
possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and
epsf style files. For additional information about SNO see
http://www.sno.phy.queensu.ca . This version has some new reference
Study of Charm Fragmentation into D^{*\pm} Mesons in Deep-Inelastic Scattering at HERA
The process of charm quark fragmentation is studied using meson
production in deep-inelastic scattering as measured by the H1 detector at HERA.
Two different regions of phase space are investigated defined by the presence
or absence of a jet containing the meson in the event. The
parameters of fragmentation functions are extracted for QCD models based on
leading order matrix elements and DGLAP or CCFM evolution of partons together
with string fragmentation and particle decays. Additionally, they are
determined for a next-to-leading order QCD calculation in the fixed flavour
number scheme using the independent fragmentation of charm quarks to
mesons.Comment: 33 pages, submitted to EPJ
Measurement of D*±, D± and Ds± meson production cross sections in pp collisions at âs=7 TeV with the ATLAS detector
The production of Dâ±, D± and D±s charmed mesons has been measured with the ATLAS detector in pp collisions at âs= 7 TeV at the LHC, using data corresponding to an integrated luminosity of 280 nbâ1. The charmed mesons have been reconstructed in the range of transverse momentum 3.5 <pT(D) <100 GeV and pseudorapidity |η(D)| <2.1. The differential cross sections as a function of transverse momentum and pseudorapidity were measured for Dâ± and D± production. The next-to-leading-order QCD predictions are consistent with the data in the visible kinematic region within the large theoretical uncertainties. Using the visible D cross sections and an extrapolation to the full kinematic phase space, the strangeness-suppression factor in charm fragmentation, the fraction of charged non-strange D mesons produced in a vector state, and the total cross section of charm production at âs= 7 TeV were derived
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