963 research outputs found
National Geodetic Satellite Program /NGSP/ Station Solutions
Results derived from short arc, orbital solution of twelve stations, PAGEOS networ
Universal Unitarity Triangle and Physics Beyond the Standard Model
We make the simple observation that there exists a universal unitarity
triangle for all models, like the SM, the Two Higgs Doublet Models I and II and
the MSSM with minimal flavour violation, that do not have any new operators
beyond those present in the SM and in which all flavour changing transitions
are governed by the CKM matrix with no new phases beyond the CKM phase. This
universal triangle can be determined in the near future from the ratio (Delta
M)_d/(Delta M)_s and sin(2 beta) measured first through the CP asymmetry in
B_d^0 to psi K_S and later in K to pi nu nubar decays. Also suitable ratios of
the branching ratios for B to X_{d,s} nu nubar and B_{d,s} to mu^+ mu^- and the
angle gamma measured by means of CP asymmetries in B decays can be used for
this determination. Comparison of this universal triangle with the
non-universal triangles extracted in each model using epsilon, (Delta M)_d and
various branching ratios for rare decays will allow to find out in a
transparent manner which of these models, if any, is singled out by experiment.
A virtue of the universal triangle is that it allows to separate the
determination of the CKM parameters from the determination of new parameters
present in the extensions of the SM considered here.Comment: 12 pages, 1 figur
Renormalization of the Cabibbo-Kobayashi-Maskawa Quark Mixing Matrix
We have investigated the present renormalization prescriptions of
Cabibbo-Kobayashi-Maskawa (CKM) matrix. When considering the prescription which
is formulated with reference to the case of zero mixing we find it doesn't
satisfy the unitary condition of the bare CKM matrix. After added a delicate
patch this problem can be solved at one-loop level. In this paper We generalize
this prescription to all loop levels and keep the unitarity of the bare CKM
matrix, simultaneously make the amplitude of an arbitrary physical process
involving quark mixing convergent and gauge independent. We also find that in
order to keep the CKM counterterms gauge independent the unitarity of the bare
CKM matrix must be preserved.Comment: has been revised, 8 pages, 1 figur
A re-analysis of the NuSTAR and XMM-Newton broad-band spectrum of Ser~X-1
Context: Ser X-1 is a well studied LMXB which clearly shows a broad iron
line. Recently, Miller et al. (2103) have presented broad-band, high quality
NuSTAR data of SerX-1.Using relativistically smeared self-consistent reflection
models, they find a value of R_in close to 1.0 R_ISCO (corresponding to 6 R_g),
and a low inclination angle, less than 10 deg. Aims: The aim of this paper is
to probe to what extent the choice of reflection and continuum models (and
uncertainties therein) can affect the conclusions about the disk parameters
inferred from the reflection component. To this aim we re-analyze all the
available public NuSTAR and XMM-Newton. Ser X-1 is a well studied source, its
spectrum has been observed by several instruments, and is therefore one of the
best sources for this study. Methods: We use slightly different continuum and
reflection models with respect to those adopted in literature for this source.
In particular we fit the iron line and other reflection features with
self-consistent reflection models as reflionx (with a power-law illuminating
continuum modified with a high energy cutoff to mimic the shape of the incident
Comptonization spectrum) and rfxconv. With these models we fit NuSTAR and
XMM-Newton spectra yielding consistent spectral results. Results: Our results
are in line with those already found by Miller et al. (2013) but less extreme.
In particular, we find the inner disk radius at about 13 R_g and an inclination
angle with respect to the line of sight of about 27 deg. We conclude that,
while the choice of the reflection model has little impact on the disk
parameters, as soon as a self-consistent model is used, the choice of the
continuum model can be important in the precise determination of the disk
parameters from the reflection component. Hence broad-band X-ray spectra are
highly preferable to constrain the continuum and disk parameters.Comment: 13 pages including 8 figures. Accepted for publication in A&
Evidence of a non-conservative mass transfer for XTE J0929-314
Context. In 1998 the first accreting millisecond pulsar, SAX J1808.4-3658,
was discovered and to date 18 systems showing coherent, high frequency (> 100
Hz) pulsations in low mass X-ray binaries are known. Since their discovery,
this class of sources has shown interesting and sometimes puzzling behaviours.
In particular, apart from a few exceptions, they are all transient with very
long X-ray quiescent periods implying a quite low averaged mass accretion rate
onto the neutron star. Among these sources, XTE J0929-314 has been detected in
outburst just once in about 15 years of continuous monitoring of the X-ray sky.
Aims. We aim to demonstrate that a conservative mass transfer in this system
will result in an X-ray luminosity that is higher than the observed, long-term
averaged X-ray luminosity. Methods. Under the hypothesis of a conservative mass
transfer driven by gravitational radiation, as expected for this system given
the short orbital period of about 43.6 min and the low mass of the companion
implied by the mass function derived from timing techniques, we calculate the
expected mass transfer rate in this system and predict the long-term averaged
X-ray luminosity. This is compared with the averaged, over 15 years, X-ray flux
observed from the system, and a lower limit of the distance to the source is
inferred. Results. This distance is shown to be > 7.4 kpc in the direction of
the Galactic anticentre, implying a large height, > 1.8 kpc, of the source with
respect to the Galactic plane, placing the source in an empty region of the
Galaxy. We suggest that the inferred value of the distance is unlikely.
(abridged)Comment: 6 pages, 2 figures, accepted for publication in Astronomy &
Astrophysics (A&A
Updating the orbital ephemeris of the dipping source XB 1254-690 and the distance to the source
XB 1254-690 is a dipping low mass X-ray binary system hosting a neutron star
and showing type I X-ray bursts. We aim at obtaining more accurate orbital
ephemeris and at constraining the orbital period derivative of the system for
the first time. In addition, we want to better constrain the distance to the
source in order to locate the system in a well defined evolutive scenario. We
apply for the first time an orbital timing technique to XB 1254-690, using the
arrival times of the dips present in the light curves that have been collected
during 26 years of X-ray pointed observations performed from different space
missions. We estimate the dip arrival times using a statistical method that
weights the count-rate inside the dip with respect to the level of the
persistent emission outside the dip. We fit the obtained delays as a function
of the orbital cycles both with a linear and a quadratic function. We infer the
orbital ephemeris of XB 1254-690 improving the accuracy of the orbital period
with respect to previous estimates. We infer a mass of M
M for the donor star, in agreement with the estimations already
present in literature, assuming that the star is in thermal equilibrium while
it transfers part of its mass via the inner Lagrangian point, and assuming a
neutron star mass of 1.4 M. Using these assumptions, we also
constrain the distance to the source, finding a value of 7.6 kpc.
Finally, we discuss the evolution of the system suggesting that it is
compatible with a conservative mass transfer driven by magnetic braking.Comment: 13 pages, 5 figures, accepted for publication in Research in
Astronomy and Astrophysics (RAA
A possible solution of the puzzling variation of the orbital period of MXB 1659-298
MXB 1659-298 is a transient neutron star Low-Mass X-ray binary system that
shows eclipses with a periodicity of 7.1 hr. The source went to outburst in
August 2015 after 14 years of quiescence. We investigate the orbital properties
of this source with a baseline of 40 years obtained combining the eight eclipse
arrival times present in literature with 51 eclipse arrival times collected
during the last two outbursts. A quadratic ephemeris does not fit the delays
associated with the eclipse arrival times and the addition of a sinusoidal term
with a period of yr is required. We infer a binary orbital
period of hr and an orbital period derivative of
s s. We show that the large orbital
period derivative can be explained with a highly non conservative mass transfer
scenario in which more than 98\% of the mass provided by the companion star
leaves the binary system. We predict an orbital period derivative value of
s s and constrain the companion star
mass between 0.3 and M. Assuming that the
companion star is in thermal equilibrium the periodic modulation can be due to
either a gravitational quadrupole coupling due to variations of the oblateness
of the companion star or with the presence of a third body of mass M
Jovian masses.Comment: 10 pages, 6 figures. Accepted by MNRA
Recent developments in radiative B decays
We report on recent theoretical progress in radiative B decays. We focus on a
calculation of logarithmically enhanced QED corrections to the branching ratio
and forward-backward asymmetry in the inclusive rare decay anti-B --> X(s) l+
l-, and present the results of a detailed phenomenological analysis. We also
report on the calculation of NNLO QCD corrections to the inclusive decay anti-B
--> X(s) gamma. As far as exclusive modes are concerned we consider
transversity amplitudes and the impact of right-handed currents in the
exclusive anti-B --> K^* l+ l- decay. Finally, we state results for exclusive B
--> V gamma decays, notably the time-dependent CP-asymmetry in the exclusive B
--> K^* gamma decay and its potential to serve as a so-called ``null test'' of
the Standard Model, and the extraction of CKM and unitarity triangle parameters
from B --> (rho,omega) gamma and B --> K^* gamma decays.Comment: 5 pages, 2 figures. Accepted for publication in the proceedings of
International Europhysics Conference on High Energy Physics (EPS-HEP2007),
Manchester, England, 19-25 Jul 200
Heavy Quark Parameters and Vcb from Spectral Moments in Semileptonic B Decays
We extract the heavy quark masses and non-perturbative parameters from the
Delphi preliminary measurements of the first three moments of the charged
lepton energy and hadronic mass distributions in semileptonic B decays, using a
multi-parameter fit. We adopt two formalisms, one of which does not rely on a
1/mc expansion and makes use of running quark masses. The data are consistent
and the level of accuracy of the experimental inputs largely determines the
present sensitivity. The results allow to improve on the uncertainty in the
extraction of Vcb.Comment: 13 pages, 2 figure
New orbital ephemerides for the dipping source 4U 1323-619: constraining the distance to the source
4U 1323-619 is a low mass X-ray binary system that shows type I X-ray bursts
and dips. The most accurate estimation of the orbital period is 2.941923(36)
hrs and a distance from the source that is lower than 11 kpc has been proposed.
We aim to obtain the orbital ephemeris, the orbital period of the system, as
well as its derivative to compare the observed luminosity with that predicted
by the theory of secular evolution. We took the advantage of about 26 years of
X-ray data and grouped the selected observations when close in time. We folded
the light curves and used the timing technique, obtaining 12 dip arrival times.
We fit the delays of the dip arrival times both with a linear and a quadratic
function. We locate 4U 1323-619 within a circular area centred at RA (J2000)=
201.6543\degree and DEC (J2000)= -62.1358\degree with an associated error of
0.0002\degree, and confirm the detection of the IR counterpart already
discussed in literature. We estimate an orbital period of P=2.9419156(6) hrs
compatible with the estimations that are present in the literature, but with an
accuracy ten times higher. We also obtain a constraint on the orbital period
derivative for the first time, estimating
s/s. Assuming that the companion star is in thermal equilibrium in the lower
main sequence, and is a neutron star of 1.4 M, we infer a mass of
0.280.03 M for the companion star. Assuming a distance of 10
kpc, we obtained a luminosity of (4.30.5) erg s,
which is not in agreement with what is predicted by the theory of secular
evolution. Using a 3D extinction map of the K radiation in our Galaxy, we
obtain a distance of 4.2 kpc at 68\% confidence level.
(Abridged)Comment: 10 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
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