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1.
Resonant active-to-active (
), as well as active-to-sterile (
) neutrino (
) oscillations can take place during the core bounce of a supernova collapse. Besides, over this phase, weak magnetism increases the antineutrino (
) mean free path, and thus its luminosity. Because the oscillation feeds mass-energy into the target
species, the large mass-squared difference between the species (
) implies a huge amount of energy to be given off as gravitational waves (
erg s-1), due to anisotropic but coherent
flow over the oscillation length. This asymmetric
-flux is driven by both the spin-magnetic and the universal spin-rotation coupling. The novel contribution of this paper stems from (1) the new computation of the anisotropy parameter
-0.01, and (2) the use of the tight constraints from neutrino experiments as SNO and KamLAND, and the cosmic probe WMAP, to compute the gravitational-wave emission during neutrino oscillations in supernovae core collapse and bounce. We show that the mass of the sterile neutrino
that can be resonantly produced during the flavor conversions makes it a good candidate for dark matter as suggested by Fuller et al. , Phys. Rev. D 68, 103002 (2003). The new spacetime strain thus estimated is still several orders of magnitude larger than those from
diffusion (convection and cooling) or quadrupole moments of neutron star matter. This new feature turns these bursts into the more promising supernova gravitational-wave signals that may be detected by observatories as LIGO, VIRGO, etc., for distances far out to the VIRGO cluster of galaxies.Received: 26 November 2003, Revised: 26 February 2004, Published online: 3 June 2004 相似文献
2.
The production of
, D0, D + , Ds + and
charm hadrons and their antiparticles in e p scattering at HERA was measured with the ZEUS detector using an integrated luminosity of
. The measurement has been performed in the photoproduction regime with the exchanged-photon virtuality
and for photon-proton centre-of-mass energies in the range
. The charm hadrons were reconstructed in the range of transverse momentum
and pseudorapidity
. The production cross sections were used to determine the ratio of neutral and charged D-meson production rates,
, the strangeness-suppression factor,
, and the fraction of charged D mesons produced in a vector state,
. The measured
and
values agree with those obtained in deep inelastic scattering and in e + e- annihilations. The measured
value is smaller than, but consistent with, the previous measurements. The fractions of c quarks hadronising as a particular charm hadron,
, were derived in the given kinematic range. The measured open-charm fragmentation fractions are consistent with previous
results, although the measured
is smaller and
is larger than those obtained in e + e- annihilations. These results generally support the hypothesis that fragmentation proceeds independently of the hard sub-process.
Received: 12 August 2005, Revised: 8 September 2005, Published online: 6 October 2005 相似文献
3.
The challenge of demonstrating that the matter produced in heavy ion collisions is a deconfined quark-gluon plasma, as predicted by lattice QCD calculations, is the challenge of measuring the number of thermodynamic degrees of freedom
at the time t0 at which the matter comes into approximate local thermal equilibrium and begins to behave like a hydrodynamic fluid. Data from experiments done at the Relativistic Heavy Ion Collider have been used to estimate t0 and to put a lower bound on the energy density
. However, measuring
has seemed out of reach, because no current data serve even as qualitative proxies for the temperature T(t0). We point out that
may equally appropriately be defined via
, where s is the entropy density, which can be estimated from the measured final state entropy. This estimate is based on the testable assumption of an isentropic expansion. The observation of jet quenching has the potential to provide an upper bound on the energy density at early times. Our goal is to motivate such an analysis by pointing out that it would set a lower bound on
.Received: 18 February 2005, Revised: 14 April 2005, Published online: 31 May 2005 相似文献
4.
Twist-3 distribution amplitudes of the pion and kaon are studied in this paper. We calculate the first several moments for the twist-3 distribution amplitudes (
and
) of the pion and kaon by applying the QCD sum rules. Our results show that (i) the first three moments of
and the first two moments of
and
of the pion and kaon can be obtained with 30
uncertainty; (ii) the fourth moment of the
and the second moment of the
can be obtained when the uncertainty are relaxed to 35
; (iii) the fourth moment of the
can be obtained only when the uncertainty are relaxed to 40
; (iv) we have
and
after including the
-corrections to the perturbative part. These moments will be helpful for constructing the twist-3 wave functions of the pion and kaon.Received: 6 January 2005, Revised: 29 March 2005, Published online: 22 June 2005PACS:
13.20.He, 11.55.Hx 相似文献
5.
This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions,
for the
process for centre-of-mass energies above the Z resonance, from
-207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study
a variety of models including the S-Matrix ansatz for
scattering and several models which include physics beyond the Standard Model: the exchange of Z′ bosons, contact interactions
between fermions, the exchange of gravitons in large extra dimensions and the exchange of
in R-parity violating supersymmetry.
This paper is dedicated to the memory of Alan Segar. 相似文献
6.
In the CP-violating minimal supersymmetric standard model (MSSM), for certain values of the CP-violating phases associated to the universal trilinear couplings (At, Ab) and the gluino mass
, e.g.,
or
, for
GeV and
-5, the lightest Higgs boson mass (
) is
GeV. This mass interval is still allowed by results of standard LEP Higgs searches because of a strongly suppressed H1ZZ coupling. However, in the same region of parameter space in which these two conditions occur, the
coupling is enhanced because the two mentioned sets of couplings satisfy a sum rule. In this paper we probe such a light Higgs scenario at the Large Hadron Collider (LHC) by studying
associate production, leading to a
signal. We show that the latter is readily accessible at the CERN hadron collider, upon the application of suitable selection cuts against the standard model (SM) backgrounds. Our parton level Monte Carlo (MC) analysis yields
-45 signal events, completely free of SM background, for
- 30 fb-1 of accumulated luminosity, after taking into account the overall efficiency for tagging four b-jets.Received: 21 February 2005, Published online: 6 July 2005 相似文献
7.
S. Y. Choi H.-U. Martyn P. M. Zerwas 《The European Physical Journal C - Particles and Fields》2005,44(2):175-182
The measurement of the trilinear couplings A in the part of the Lagrangian which breaks supersymmetry softly will be a difficult experimental task. In this report the
heavy Higgs decays
to stau pairs are investigated for measuring the stau trilinear coupling
. Based on detailed simulations of signal and backgrounds for a specific reference point in future high luminosity e + e- linear collider experiments, it is concluded that the parameter
can be determined with a precision at the 10% level in the region of moderate to large
.
Received: 2 August 2005, Published online: 13 September 2005 相似文献
8.
Multijet production rates in neutral current deep inelastic scattering have been measured in the range of exchanged boson
virtualities
. The data were taken at the ep collider HERA with centre-of-mass energy
using the ZEUS detector and correspond to an integrated luminosity of
. Jets were identified in the Breit frame using the kT cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential dijet and trijet cross sections
are presented as functions of jet transverse energy (
), pseudorapidity (
) and Q2 with
and
. Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant
, determined from the ratio of the trijet to dijet cross sections, is
.
Received: 1 April 2005, Revised: 28 June 2005, Published online: 30 August 2005 相似文献
9.
The most precise measurement of the weak mixing angle
at LEP is from the forward-backward asymmetry
at the Z-pole. In this note the QED and electroweak radiative corrections to obtain the pole asymmetry from the measured asymmetry for b- and c-quarks have been calculated using ZFITTER, which has been amended to allow a consistent treatment of partial two-loop corrections for the b-quark final asymmetries. A total correction of
and
has been found, where the remaining theoretical uncertainty is much too small to explain the apparent discrepancy between
obtained from A
FB
b
and from the left-right asymmetry at SLD.Received: 1 December 2004, Published online: 9 March 2005 相似文献
10.
production in
interactions has been detected via its decays into
,K
+
K
-
K
+
K
- and
in the data taken with the DELPHI detector at LEP1 and LEP2 energies. The two-photon radiative width averaged over all observed decay channels is
= 13.9
2.0 (stat.)
1.4(syst.)
2.7 (BR) keV. No direct decay channel
has been observed. An upper limit
< 5.5 keV at 95% confidence level has been evaluated for this decay mode.Received: 3 July 2003, Published online: 7 November 2003 相似文献
11.
Jian-Feng Cheng Dong-Sheng Du Cai-Dian Lü 《The European Physical Journal C - Particles and Fields》2006,45(3):711-720
We investigate the branching ratios and direct CP-asymmetries of the
and
decays in the PQCD approach. All the diagrams with emission topology or annihilation topology are calculated strictly. A
branching ratio of 10-6 and 10-7 for
and
decay is predicted, respectively. Because of the different weak phase and strong phase from penguin operator and two kinds
of tree operator contributions, we predict a possible large direct CP-violation:
and
when γ = 55°, which can be tested in the coming LHC.
PACS:
13.25.Hw, 12.38.Bx 相似文献
12.
In the SUSY SO(10) GUT context, we study the exclusive processes
. Using the Wilson coefficients of the relevant operators including the new operators
which are induced by neutral Higgs boson (NHB) penguins, we evaluate some possible observables associated with these processes like the invariant mass spectrum (IMS), lepton pair forward-backward asymmetry (FBA), lepton polarization asymmetries etc. In this model the contributions from Wilson coefficients
, among new contributions, are dominant. Our results show that the NHB effects are sensitive to the FBA,
, and
of
decay, which are expected to be measured in B factories, the deviation of
in
can reach 0.1 from SM, which could be seen in B factories, and the average of the normal polarization
can reach several percent for
and it is 0.05 or so for
, which could be measured in the future super B factories and provide useful information to probe new physics and discriminate different models.Received: 30 October 2004, Published online: 9 March 2005 相似文献
13.
M. Dubinin H. J. Schreiber A. Vologdin 《The European Physical Journal C - Particles and Fields》2003,30(3):337-344
We examine the prospects for measuring the
coupling of a standard model-like Higgs boson with a mass between 120 and 160 GeV at the future TESLA linear e
+
e
- collider, assuming an integrated luminosity of 1 ab-1 and a center-of-mass energy of 500 GeV. We consider the Higgs boson produced in association with
via the W W fusion reaction
, followed by the rare decay into a Z boson and a photon,
. Accounting for all main background contributions, a precision of 27% can be achieved in unpolarized e
+
e
- collisions for M
H
= 140 GeV. With appropriate initial state polarisations
BF(
)/BF(
), or the precisions on the
partial width, can be improved to 17% and provide valuable information on the
coupling. For M
H
= 120 and 160 GeV, the small significance of the signals in unpolarized collisions sets upper limits of 79% respectively 72% at 90% confidence level on the
branching fraction.Received: 5 March 2003, Revised: 14 July 2003, Published online: 5 September 2003 相似文献
14.
15.
Upper limits on the cross-section of the pair-production process
, assuming 100
branching fraction to hadrons, are derived from a new search for the
hadrons final state, independently of the hadronic flavour of the decay products. This study, combined with previously published searches for the neutral Higgs bosons h0 and A0, is used to constrain the Type II Two Higgs Doublet Model (2HDM(II)) with no CP violation in the Higgs sector and no additional non-Standard Model particles besides the five Higgs bosons. The analysis combines LEP1 and LEP2 data collected with the OPAL detector up to the highest available centre-of-mass energies. The searches are sensitive to the
and
decay modes of the Higgs bosons. A benchmark scan of the 2HDM(II) parameter space is performed. Large regions of the 2HDM(II) parameter space explored are excluded at the 95% CL in the (
and
planes, using both direct neutral Higgs boson searches and indirect limits derived from Standard Model high precision measurements. The region
GeV and
GeV is excluded at 95 % CL, independently of
and for selected values of
which are representative of a complete
-scan.Received: 28 July 2004, Revised: 4 January 2005, Published online: 3 March 2005 相似文献
16.
M. Beneke Th Feldmann D. Seidel 《The European Physical Journal C - Particles and Fields》2005,41(2):173-188
We provide standard model expectations for the rare radiative decays
,
and
, and the electroweak penguin decays
and
at the next-to-leading order (NLO), extending our previous results to
transitions. We consider branching fractions, isospin asymmetries and direct CP asymmetries. For the electroweak penguin decays, the lepton-invariant mass spectrum and forward-backward asymmetry is also included. Radiative and electroweak penguin transitions in
are mainly interesting in the search for new flavor-changing neutral current interactions, but in addition the
decays provide constraints on the CKM parameters
. The potential impact of these constraints is discussed.Received: 16 January 2005, Published online: 16 March 2005
Corresponding author: Th. Feldmann 相似文献
17.
The COMPASS Collaboration 《The European Physical Journal C - Particles and Fields》2005,41(4):469-474
Narrow
and
resonances produced by quasi-real photons have been searched for by the COMPASS experiment at CERN. The study was stimulated by the recent observation of an exotic baryonic state decaying into
, at a mass of 1862 MeV, interpreted as a pentaquark. While the ordinary hyperon states
and
are clearly seen, no exotic baryon is observed in the data taken in 2002 and 2003.Received: 15 March 2005, Published online: 31 May 2005PACS:
13.60.Hb, 13.60.Rj, 14.20.Jn, 14.80.-j 相似文献
18.
The one-loop contributions to the branching ratios for leptonic
decays are calculated in the CP-conserving 2HDM(II). The analysis is focused on large
enhanced contributions. We found that these contributions, involving loops with both neutral and charged Higgs bosons, dominate
over the tree-level
exchange, the latter one being totally negligible for the decay into e. We derive a simple analytical expression for the one-loop contribution which holds in the large
case. We show that the leptonic branching ratios of
are complementary to the Higgsstrahlung processes for h(H) and have a large potential in constraining the parameters of the model. In this work we provide upper limits on the Yukawa
couplings for both light h and light A scenarios, and we derive a new lower limit on the mass of
as a function of
which differs significantly from what was considered as a standard constraint based on the tree-level
exchange only. Interestingly we also obtain an upper limit on
.
Received: 22 February 2005, Revised: 12 July 2005, Published online: 6 October 2005
D. Temes: * UMR 5108 du CNRS, associée á l'Université de Savoie. 相似文献
19.
We compute the one-loop
-functions describing the renormalisation of the coupling constant
and the frequency parameter
for the real four-dimensional duality-covariant non-commutative
-model, which is renormalisable to all orders. The contribution from the one-loop four-point function is reduced by the one-loop wavefunction renormalisation, but the
-function remains non-negative. Both
and
vanish at the one-loop level for the duality-invariant model characterised by
. Moreover,
also vanishes in the limit
, which defines the standard non-commutative
-quantum field theory. Thus, the limit
exists at least at the one-loop level.Received: 19 March 2004, Published online: 5 May 2004 相似文献
20.
H. K. Wöhri 《The European Physical Journal C - Particles and Fields》2005,43(1-4):407-413
During the June 2002 run NA60 collected around 600 000 dimuon triggers in proton-nucleus collisions at 400 GeV. We show that
the collected dimuon mass spectra can be understood in terms of known sources. The specific target setup, consisting of Beryllium,
Indium and Lead targets, simultaneously exposed to the beam, allowed us to study the nuclear dependence of the production
cross-section of the
and
resonances. The elementary nucleon-nucleon production cross-sections at 400 GeV for the
,
and
mesons are also presented. By using the
-Dalitz decay, dominating the mass range below 450 MeV, we, furthermore, extracted the
production cross-section and its nuclear dependence. The results are discussed in the framework of previous measurements,
mostly obtained in different decay channels, performed by NA27, HELIOS-1 and CERES-TAPS.
Arrival of the final proofs: 1 July 2005
PACS:
25.75.Dw, 25.75.Nq 相似文献