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1.
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
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 Standard Model constraints on
which can be derived from the
decays are revisited in some depth. As experimental inputs, the
,
decays complemented by the
decays, the CP parameters
and
, and/or the value of
as determined by the global CKM fit are used. The constraints discussed here are model independent in the sense that they rely only on Isospin symmetry, following the Gronau-London proposal. A new bound on
and the function
are introduced. While another bound applied to BABAR results is shown to imply that
is negative. The Grossman-Quinn bound is rediscussed. A close form expression is given for
as a function of the measurements. Various scenarios for the future of the isospin analysis are explored. To probe the Standard Model the
plane is introduced.Received: 17 December 2004, Published online: 25 January 2005 相似文献
4.
The anomalous weak dipole moments of the
lepton are measured in a data sample collected by ALEPH from 1990 to 1995 corresponding to an integrated luminosity of 155 pb-1. Tau leptons produced in the reaction
at energies close to the
mass are studied using their semileptonic decays to
,
,
or
. The real and imaginary components of both the anomalous weak magnetic dipole moment and the CP-violating anomalous weak electric dipole moment,
,
,
and
, are measured simultaneously by means of a likelihood fit built from the full differential cross section. No evidence of new physics is found. The following bounds are obtained (95% CL):
,
,
, and
.Received: 25 September 2002, Published online: 29 August 2003 相似文献
5.
R. Tomaschitz 《The European Physical Journal C - Particles and Fields》2006,45(2):493-511
We study superluminal cyclotron emission by electrons and muons in semiclassical orbits. The tachyonic line spectra of hydrogenic
ions such as
,
, and
, as well as their muonic counterparts
,
and
are calculated, in particular the tachyonic power transversally and longitudinally radiated, the total intensity, and the
power radiated in the individual harmonics. We also investigate tachyonic continuum radiation from electrons and protons cycling
in the surface and light cylinder fields of
-ray and millisecond pulsars, such as the Crab pulsar, PSR B1509-58, and PSR J0218 + 4232. The superluminal spectral densities
generated by non-relativistic, mildly relativistic and ultra-relativistic source particles are derived. We study the parameters
determining the global shape of the transversal and longitudinal densities and the energy scales of the broadband spectrum.
The observed cutoff frequency in the
-ray band of the pulsars is used to infer the upper edge of the orbital energy, and we conclude that electrons and nuclei
cycling in the surface fields can reach energies beyond the "ankle" of the cosmic ray spectrum. This suggests
-ray pulsars as sources of ultra-high energy cosmic rays.
Arrival of the final proofs: 17 November 2005
PACS:
41.60.Ap, 11.10.Lm, 36.10.Dr, 98.70.Sa 相似文献
6.
A search for lepton-flavor-violating interactions
and
has been performed with the ZEUS detector using the entire HERA I data sample, corresponding to an integrated luminosity
of
. The data were taken at center-of-mass energies,
, of 300 and
. No evidence of lepton-flavor violation was found, and constraints were derived on leptoquarks (LQs) that could mediate such
interactions. For LQ masses below
, limits were set on
, where
is the coupling of the LQ to an electron and a first-generation quark q1, and
is the branching ratio of the LQ to the final-state lepton
(μ or
) and a quark q. For LQ masses much larger than
, limits were set on the four-fermion interaction term
for LQs that couple to an electron and a quark
and to a lepton
and a quark
, where
and
are quark generation indices. Some of the limits are also applicable to lepton-flavor-violating processes mediated by squarks
in R-Parity-violating supersymmetric models. In some cases, especially when a higher-generation quark is involved and for the
process
, the ZEUS limits are the most stringent to date.
Received: 1 April 2005, Revised: 13 July 2005, Published online: 18 October 2005 相似文献
7.
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
8.
H. Buesching 《The European Physical Journal C - Particles and Fields》2005,43(1-4):303-310
Transverse momentum (
) spectra measured by the PHENIX experiment at RHIC in Au + Au, d + Au and pp collisions at
and in Au + Au collisions at
are presented. A suppression of the yield of high
hadrons in central Au + Au collisions by a factor 4-5 at
is found relative to the pp reference scaled by the nuclear overlap function
. In contrast, direct photons are not suppressed in central Au + Au collisions and no suppression of high
particles can be seen in d + Au collisions. This leads to the conclusion that the dense medium formed in central Au + Au
collisions is responsible for the suppression.
Arrival of the final proofs: 30 June 2005
PACS:
25.75.Dw 相似文献
9.
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
10.
In the minimal supersymmetric standard model (MSSM), we study the light Higgs boson radiation off a light-chargino pair in the process
at linear colliders with
GeV. We analyze cross sections in the regions of the MSSM parameter space where the process
cannot proceed via on-shell production and subsequent decay of either heavier charginos or the pseudoscalar Higgs boson A. Cross sections up to a few fb are allowed, according to present experimental limits on the Higgs boson, chargino and sneutrino masses. We also show how a measurement of the
production rate could provide a determination of the Higgs boson couplings to charginos.Received: 24 June 2004, Revised: 13 May 2005, Published online: 19 July 2005 相似文献
11.
《The European Physical Journal C - Particles and Fields》2004,37(4):421-431
The Pauli exclusion principle (PEP) has been tested for nucleons (n,p) in
and
nuclei, using the results of background measurements with the prototype of the Borexino detector, the Counting Test Facility (CTF). The approach consisted of a search for
, n, p and/or
s emitted in a non-Paulian transition of 1P- shell nucleons to the filled 1S
1/2 shell in nuclei. Similarly, the Pauli-forbidden
decay processes were searched for. Due to the extremely low background and the large mass (4.2 tons) of the CTF detector, the following most stringent up-to-date experimental bounds on PEP violating transitions of nucleons have been established:
,
,
,
,
and
, all at
C.L.Received: 18 June 2004, Published online: 1 October 2004PACS:
11.30.-j, 24.80. + y, 23.20.-g, 27.20. + nG. Bellini: SpokesmanL. Cadonati: Now at Massachusetts Institute of Technology, NW17-161, 175 Albany St. Cambridge, MA 02139O. Dadoun: Marie Curie fellowship at LNGS
Correspondence to: A. Derbin. On leave of absence from St. Petersburg Nuclear Physics Inst. - Gatchina, RussiaM. Deutsch: DeceasedR. Ford: No w at Sudbury Neutrino Observatory, INCO Creighton Mine, P.O.Box 159 Lively, Ontario, Canada, P3Y 1M3B. Freudiger: Marie Curie fellowship at LNGS. Now at Institute for Nuclear Physics, Forschungszentrum Karlsruhe, Postfach 3640, 76021 KarlsruheS. Gazzana: GLIMOSV.V. Kobychev: Now at Institute for Nuclear Research, Prospekt Nauki 47, MSP 03680, Kiev, UkraineG. Korga: On leave of absence from KFKI-RMKI, Konkoly Thege ut 29-33 H-1121 Budapest, HungaryC. Lendvai: Marie Curie fellowship at LNGSP. Lombardi: Detector installation managerA. Martemianov: DeceasedV. Muratova: On leave of absence from St. Petersburg Nuclear Physics Inst. - Gatchina, RussiaL. Niedermeier: Marie Curie fellowship at LNGSL. Papp: On leave of absence from KFKI-RMKI, Konkoly Thege ut 29-33 H-1121 Budapest, HungaryR.S. Raghavan: Present Address: Department of Physics, Virginia Polytechnic Institute and State University, Blacksburg VA 24061G. Ranucci: Project managerC. Salvo: Operational manager
Correspondence to: O. SmirnovA. Sonnenschein: Center for Cosmological Physics, University of Chicago, 933 E.56th St., Chicago, IL 60637 相似文献
12.
Hubaut F. Monnier E. Pralavorio P. Smolek K. Simak V. 《The European Physical Journal C - Particles and Fields》2005,44(1):13-25
The inelastic production of
mesons in ep collisions has been studied with the ZEUS detector at HERA using an integrated luminosity of
. The
mesons were identified using the decay channel
. The measurements were performed in the kinematic range
,
, 0.2 < z < 0.9 and
, where Q2 is the virtuality of the exchanged photon, W is the photon-proton centre-of-mass energy, z is the fraction of the photon energy carried by the
meson in the proton rest frame and
is the rapidity of the
in the laboratory frame. The measured cross sections are compared to theoretical predictions within the non-relativistic QCD framework including colour-singlet and colour-octet contributions, as well as to predictions based on the kT-factorisation approach. Calculations of the colour-singlet process generally agree with the data, whereas inclusion of colour-octet terms spoils this agreement.Received: 18 May 2005, Revised: 24 June 2005, Published online: 27 July 2005 相似文献
13.
J. Bielcikova 《The European Physical Journal C - Particles and Fields》2005,43(1-4):323-327
A study of elliptic flow and two-particle azimuthal correlations of charged particles (
GeV/c) and high-
pions (
GeV/c) in Pb + Au collisions at 158A GeV/c, close to midrapidity, is presented. Elliptic flow (v
2) rises linearly with
to a value of about 10
at 2 GeV/c. Beyond
1.5 GeV/c, the slope decreases and possibly indicates a v
2 saturation at high
. Two-pion azimuthal anisotropies for
1.2 GeV/c exceed the v
2 values by about 60
in semicentral collisions. This non-flow component is attributed to near-side and away-side jetlike correlations. While the
near-side peak remains constant with centrality 0.23
0.03 rad, as expected for fragmentation, the away-side peak experiences broadening and disappears in central collisions.
Arrival of the final proofs: 30 June 2005
PACS:
25.75.Ld, 25.75.Gz 相似文献
14.
M. Neubert 《The European Physical Journal C - Particles and Fields》2005,40(2):165-186
Using results on soft-collinear factorization for inclusive B-meson decay distributions, a systematic study of the partial
decay rate with a cut
on photon energy is performed. For values of E
0 below about 1.9 GeV, the rate can be calculated without reference to shape functions using a multi-scale operator product expansion (MSOPE). The transition from the shape-function region to the MSOPE region is studied analytically. The resulting prediction for the
branching ratio depends on three large scales: m
b
,
, and
. Logarithms associated with these scales are resummed at next-to-next-to-leading logarithmic order. While power corrections in
turn out to be small, the sensitivity to the scale
GeV (for
GeV) introduces significant perturbative uncertainties, which so far have been ignored. The new theoretical prediction for the
branching ratio with
GeV is
, where the first error is an estimate of perturbative uncertainties and the second one reflects uncertainties in input parameters. With this cut
of all events are contained. When this fraction is combined with the previously best prediction for the total decay rate, one obtains
, with a somewhat less conservative estimate of parametric uncertainties. The implications of larger theory uncertainties for new physics searches are briefly explored with the example of the type-II two-Higgs-doublet model, for which the lower bound on the charged-Higgs mass is reduced compared with previous estimates to approximately 200 GeV at 95% confidence level.Received: 18 September 2004, Revised: 18 January 2005, Published online: 21 February 2005 相似文献
15.
The L Collaboration 《The European Physical Journal C - Particles and Fields》2005,40(3):333-341
Data collected at LEP at centre-of-mass energies
GeV are used to study correlations of the spin of W bosons using
events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in
and
events. Decay-plane correlations are measured to be consistent with the Standard Model predictions.Received: 26 October 2004, Revised: 15 January 2005, Published online: 3 March 2005 相似文献
16.
A. Mischke 《The European Physical Journal C - Particles and Fields》2005,43(1-4):311-316
In this paper, preliminary results are presented on high
inclusive neutral pion measurements in d-Au collisions at
GeV in the pseudo-rapidity range
. Photons from the decay
are detected in the Barrel Electromagnetic Calorimeter of the STAR experiment at RHIC. The analysis of this first BEMC hadron
measurement is described in detail. The results are compared to earlier RHIC findings. Furthermore, the obtained
invariant differential cross sections show good agreement with next-to-leading order (NLO) perturbative QCD calculations.
Arrival of the final proofs: 4 July 2005
PACS:
25.75.-q 相似文献
17.
A measurement is presented of elastic deeply virtual Compton scattering
made using e + p collision data corresponding to a luminosity of 46.5 pb-1, taken with the H1 detector at HERA. The cross section is measured as a function of the photon virtuality, Q 2, the invariant mass of the
p system, W, and for the first time, differentially in the squared momentum transfer at the proton vertex, t, in the kinematic range
,
and
. QCD based calculations at next-to-leading order using generalized parton distributions can describe the data, as can colour dipole model predictions.Received: 19 May 2005, Revised: 23 June 2005, Published online: 19 August 2005 相似文献
18.
The tau lepton lifetime has been measured with the
events collected by the DELPHI detector at LEP in the years 1991-1995. Three different methods have been exploited, using both one-prong and three-prong
decay channels. Two measurements have been made using events in which both taus decay to a single charged particle. Combining these measurements gave
. A third measurement using taus which decayed to three charged particles yielded
These were combined with previous DELPHI results to measure the tau lifetime, using the full LEP1 data sample, to be
.Received: 12 November 2003, Revised: 1 June 2004, Published online: 20 July 2004 相似文献
19.
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
20.
A new evaluation of the hadronic vacuum polarization contribution to the muon magnetic moment is presented. We take into account the reanalysis of the low-energy e
+
e
-annihilation cross section into hadrons by the CMD-2 Collaboration. The agreement between e
+
e
-and
spectral functions in the
channel is found to be much improved. Nevertheless, significant discrepancies remain in the center-of-mass energy range between 0.85 and
, so that we refrain from averaging the two data sets. The values found for the lowest-order hadronic vacuum polarization contributions are
where the errors have been separated according to their sources: experimental, missing radiative corrections in e
+
e
-data, and isospin breaking. The corresponding Standard Model predictions for the muon magnetic anomaly read
where the errors account for the hadronic, light-by-light (LBL) scattering and electroweak contributions. The deviations from the measurement at BNL are found to be
(1.9
) and
(0.7
) for the e
+
e
-- and
-based estimates, respectively, where the second error is from the LBL contribution and the third one from the BNL measurement.Received: 7 September 2003, Published online: 30 October 2003 相似文献