493 research outputs found
Hawking Radiation as Quantum Tunneling in Rindler Coordinate
We substantiate the Hawking radiation as quantum tunneling of fields or
particles crossing the horizon by using the Rindler coordinate. The thermal
spectrum detected by an accelerated particle is interpreted as quantum
tunneling in the Rindler spacetime. Representing the spacetime near the horizon
locally as a Rindler spacetime, we find the emission rate by tunneling, which
is expressed as a contour integral and gives the correct Boltzmann factor. We
apply the method to non-extremal black holes such as a Schwarzschild black
hole, a non-extremal Reissner-Nordstr\"{o}m black hole, a charged Kerr black
hole, de Sitter space, and a Schwarzschild-anti de Sitter black hole.Comment: LaTex 19 pages, no figure; references added and replaced by the
version accepted in JHE
Implications of recent solar neutrino observations: an analysis of charged current data
We have analysed the recent results from the observation of charged current
\nu_e d \to e^- p p events from solar neutrinos by the Sudbury Neutrino
Observatory SNO assuming neutrino oscillations with three active flavours. The
data seem to prefer a low mass-squared difference and large mixing angle
solution (the so-called LOW solution) in (12) parameter space. However, when
combined with the Gallium charged current interaction data from Gallex and GNO,
distinct (1\sigma) allowed regions corresponding to the large mixing angle
(LMA) and small mixing angle (SMA) appear while the LOW solution is disfavoured
upto 3\sigma standard deviation. The physical electron neutrino survival
probability corresponding to these best fit solutions are then determined and
analysed for their energy dependence.Comment: 16 pages Latex file, with 5 epsf figures; one reference adde
14Be(p,n)14B reaction at 69 MeV in inverse kinematics
A Gamow-Teller (GT) transition from the drip-line nucleus 14Be to 14B was
studied via the (p,n) reaction in inverse kinematics using a secondary 14Be
beam at 69 MeV/nucleon. The invariant mass method is employed to reconstruct
the energy spectrum. A peak is observed at an excitation energy of 1.27(2) MeV
in 14B, together with bumps at 2.08 and 4.06(5) MeV. The observed forward
peaking of the state at 1.27 MeV and a good description for the differential
cross section, obtained with a DWBA calculation provide support for the 1+
assignment to this state. By extrapolating the cross section to zero momentum
transfer the GT-transition strength is deduced. The value is found to compare
well with that reported in a beta-delayed neutron emission study.Comment: 5 pages, 2 figure
Status of a Supersymmetric Flavour Violating Solution to the Solar Neutrino Puzzle with Three Generations
We present a general study of a three neutrino flavour transition model based
on the supersymmetric interactions which violate R-parity. These interactions
induce flavour violating scattering reactions between solar matter and
neutrinos. The model does not contain any vacuum mass or mixing angle for the
first generation neutrino. Instead, the effective mixing in the first
generation is induced via the new interactions. The model provides a natural
interpretation of the atmospheric neutrino anomaly, and is consistent with
reactor experiments. We determine all R-parity violating couplings which can
contribute to the effective neutrino oscillations, and summarize the present
laboratory bounds. Independent of the specific nature of the (supersymmetric)
flavour violating model, the experimental data on the solar neutrino rates and
the recoil electron energy spectrum are inconsistent with the theoretical
predictions. The confidence level of the -analysis ranges between and . The incompatibility, is due to the new SNO
results, and excludes the present model. We conclude that a non-vanishing
vacuum mixing angle for the first generation neutrino is necessary in our
model. We expect this also to apply to the solutions based on other flavour
violating interactions having constraints of the same order of magnitude.Comment: 17 pages, Latex fil
Three-generation flavor transitions and decays of supernova relic neutrinos
If neutrinos have mass, they can also decay. Decay lifetimes of cosmological
interest can be probed, in principle, through the detection of the redshifted,
diffuse neutrino flux produced by all past supernovae--the so-called supernova
relic neutrino (SRN) flux. In this work, we solve the SRN kinetic equations in
the general case of three-generation flavor transitions followed by invisible
(nonradiative) two-body decays. We then use the general solution to calculate
observable SRN spectra in some representative decay scenarios. It is shown
that, in the presence of decay, the SRN event rate can basically span the whole
range below the current experimental upper bound--a range accessible to future
experimental projects. Radiative SRN decays are also briefly discussed.Comment: 25 pages, including 7 figure
Model Independent Information On Solar Neutrino Oscillations
We present the results of a Bayesian analysis of solar neutrino data in terms
of nu_e->nu_{mu,tau} oscillations, independent from the Standard Solar Model
predictions for the solar neutrino fluxes. We show that such a model
independent analysis allows to constraint the values of the neutrino mixing
parameters in limited regions around the usual SMA, LMA, LOW and VO regions.
Furthermore, there is a strong indication in favor of large neutrino mixing and
large values of Delta m^2 (LMA region). We calculate also the allowed ranges of
the neutrino fluxes and we show that they are in good agreement with the
Standard Solar Model prediction. In particular, the ratio of the 8B flux with
its Standard Solar Model prediction is constrained in the interval [0.45,1.42]
with 99.73% probability. Finally, we show that the hypothesis of no neutrino
oscillations is strongly disfavored in a model independent way with respect to
the hypothesis of neutrino oscillations.Comment: 40 pages, 20 figures. Added references and improved figure
Heavy Quarks and Heavy Quarkonia as Tests of Thermalization
We present here a brief summary of new results on heavy quarks and heavy
quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma
Thermalization" Workshop in Vienna, Austria in August 2005, directly following
the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop
(Vienna August 2005) Proceeding
Nuclear Modification of Electron Spectra and Implications for Heavy Quark Energy Loss in Au+Au Collisions at sqrt(s_NN)=200 GeV
The PHENIX experiment has measured mid-rapidity transverse momentum spectra
(0.4 < p_T < 5.0 GeV/c) of electrons as a function of centrality in Au+Au
collisions at sqrt(s_NN)=200 GeV. Contributions from photon conversions and
from light hadron decays, mainly Dalitz decays of pi^0 and eta mesons, were
removed. The resulting non-photonic electron spectra are primarily due to the
semi-leptonic decays of hadrons carrying heavy quarks. Nuclear modification
factors were determined by comparison to non-photonic electrons in p+p
collisions. A significant suppression of electrons at high p_T is observed in
central Au+Au collisions, indicating substantial energy loss of heavy quarks.Comment: 330 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Single Electrons from Heavy Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV
The invariant differential cross section for inclusive electron production in
p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment
at the Relativistic Heavy Ion Collider over the transverse momentum range $0.4
<= p_T <= 5.0 GeV/c at midrapidity (eta <= 0.35). The contribution to the
inclusive electron spectrum from semileptonic decays of hadrons carrying heavy
flavor, i.e. charm quarks or, at high p_T, bottom quarks, is determined via
three independent methods. The resulting electron spectrum from heavy flavor
decays is compared to recent leading and next-to-leading order perturbative QCD
calculations. The total cross section of charm quark-antiquark pair production
is determined as sigma_(c c^bar) = 0.92 +/- 0.15 (stat.) +- 0.54 (sys.) mb.Comment: 329 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Collectivity of neutron-rich Ti isotopes
The structure of the neutron-rich nucleus 58Ti was investigated via proton inelastic scattering in inverse kinematics at a mean energy of 42.0 MeV/nucleon. By measuring the deexcitation γ rays, three transitions with the energies of 1046(11) keV, 1376(18) keV, and 1835(27) keV were identified. The angle-integrated cross section for the 1046-keV excitation, which corresponds to the decay from the first 2+ state, was determined to be 13(7) mb. The deformation length δp,p′ was extracted from the cross section to be 0.83−0.30+0.22 fm. The energy of the first 2+ state and the δp,p′ value are comparable to the ones of 56Ti, which indicates that the collectivity of the Ti isotopes does not increase significantly with neutron number until N=36. This fact indicates that 58Ti is outside of the region of the deformation known in the neutron-rich nuclei around N=40
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