715 research outputs found
Fundamental Performance of a Dispersed Fixed Delay Interferometer In Searching For Planets Around M Dwarfs
We present a new method to calculate fundamental Doppler measurement limits
with a dispersed fixed-delay interferometer (DFDI) in the near infrared
wavelength region for searching for exoplanets around M dwarfs in the coming
decade. It is based on calculating the Q factor, a measure of flux-normalized
Doppler sensitivity in the fringing spectra created with DFDI. We calculate the
Q factor as a function of spectral resolution R, stellar projected rotational
velocity V sini, stellar effective temperature T_eff and optical path
difference (OPD) of the interferometer. We also compare the DFDI Q factor to
that for the popular cross-dispersed echelle spectrograph method (the direct
echelle (DE) method). Given the IR Doppler measurement is likely to be
detector-limited for a while, we introduce new merit functions, which is
directly related to photon-limited RV uncertainty, to evaluate Doppler
performance with the DFDI and DE methods. We find that DFDI has strength in
wavelength coverage and multi-object capability over the DE for a limited
detector resource. We simulate the performance of the InfraRed Exoplanet
Tracker (IRET) based on the DFDI design, being considered for the next
generation IR Doppler measurements. The predicted photon-limited RV uncertainty
suggests that IRET is capable of detecting Earth-like exoplanets in habitable
zone around nearby bright M dwarfs if they exist. A new method is developed to
quantitatively estimate the influence of telluric lines on RV uncertainty. Our
study shows that photon-limited RV uncertainty can be reached if 99% of the
strength of telluric lines can be removed from the measured stellar spectra. At
low to moderate levels of telluric line strength removal (50% to 90%), the
optimal RV uncertainty is typically a factor of 2-3 times larger than
photon-limited RV uncertainty.Comment: 43 pages, 20 figures, 6 tables. Accepted by Ap
Equilibrium thermodynamics in modified gravitational theories
We show that it is possible to obtain a picture of equilibrium thermodynamics
on the apparent horizon in the expanding cosmological background for a wide
class of modified gravity theories with the Lagrangian density ,
where is the Ricci scalar and is the kinetic energy of a scalar field
. This comes from a suitable definition of an energy momentum tensor of
the "dark" component that respects to a local energy conservation in the Jordan
frame. In this framework the horizon entropy corresponding to equilibrium
thermodynamics is equal to a quarter of the horizon area in units of
gravitational constant , as in Einstein gravity. For a flat cosmological
background with a decreasing Hubble parameter, globally increases with
time, as it happens for viable inflation and dark energy models. We also
show that the equilibrium description in terms of the horizon entropy is
convenient because it takes into account the contribution of both the horizon
entropy in non-equilibrium thermodynamics and an entropy production
term.Comment: 11 pages, 2 figures, version to appear in Physics Letters B, typos
correcte
The Revised TESS Input Catalog and Candidate Target List
We describe the catalogs assembled and the algorithms used to populate the
revised TESS Input Catalog (TIC), based on the incorporation of the Gaia second
data release. We also describe a revised ranking system for prioritizing stars
for 2-minute cadence observations, and assemble a revised Candidate Target List
(CTL) using that ranking. The TIC is available on the Mikulski Archive for
Space Telescopes (MAST) server, and an enhanced CTL is available through the
Filtergraph data visualization portal system at the URL
http://filtergraph.vanderbilt.edu/tess_ctl.Comment: 30 pages, 16 figures, submitted to AAS Journals; provided to the
community in advance of publication in conjunction with public release of the
TIC/CTL on 28 May 201
Evidence for the Decay
We present a search for the ``wrong-sign'' decay D0 -> K+ pi- pi+ pi- using 9
fb-1 of e+e- collisions on and just below the Upsilon(4S) resonance. This decay
can occur either through a doubly Cabibbo-suppressed process or through mixing
to a D0bar followed by a Cabibbo-favored process. Our result for the
time-integrated wrong-sign rate relative to the decay D0 -> K- pi+ pi- pi+ is
(0.0041 +0.0012-0.0011(stat.) +-0.0004(syst.))x(1.07 +-0.10)(phase space),
which has a statistical significance of 3.9 standard deviations.Comment: 9 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to PR
Hadronic Mass Moments in Inclusive Semileptonic B Meson Decays
We have measured the first and second moments of the hadronic mass-squared
distribution in B -> X_c l nu, for P(lepton) > 1.5 GeV/c. We find <M_X^2 -
M_D[Bar]^2> = 0.251 +- 0.066 GeV^2, )^2 > = 0.576 +- 0.170
GeV^4, where M_D[Bar] is the spin-averaged D meson mass.
From that first moment and the first moment of the photon energy spectrum in
b -> s gamma, we find the HQET parameter lambda_1 (MS[Bar], to order 1/M^3 and
beta_0 alpha_s^2) to be -0.24 +- 0.11 GeV^2. Using these first moments and the
B semileptonic width, and assuming parton-hadron duality, we obtain |V_cb| =
0.0404 +- 0.0013.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to PR
Observation of the Charmed Baryon at CLEO
The CLEO experiment at the CESR collider has used 13.7 fb of data to
search for the production of the (css-ground state) in
collisions at {\rm GeV}. The modes used to
study the are ,
, , , and
. We observe a signal of 40.49.0(stat) events
at a mass of 2694.62.6(stat)1.9(syst) {\rm MeV/}, for all modes
combined.Comment: 10 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Observation of and
We have studied two-body charmless hadronic decays of mesons into the
final states phi K and phi K^*. Using 9.7 million pairs collected
with the CLEO II detector, we observe the decays B- -> phi K- and B0 -> phi K*0
with the following branching fractions: BR(B- -> phi K-)=(5.5 +2.1-1.8 +- 0.6)
x 10^{-6} and BR(B0 -> phi K*0)=(11.5 +4.5-3.7 +1.8-1.7) x 10^{-6}. We also see
evidence for the decays B0 -> phi K0 and B- -> phi K*-. However, since the
statistical significance is not overwhelming for these modes we determine upper
limits of <12.3 x 10^{-6} and <22.5 x 10^{-6} (90% C.L.) respectively.Comment: 9 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Evidence of New States Decaying into
Using 13.7 of data recorded by the CLEO detector at CESR, we report
evidence for two new charmed baryons: one decaying into
with the subsequent decay , and its
isospin partner decaying into followed by
. We measure the following mass differences
for the two states: =318.2+-1.3+-2.9 MeV,
and =324.0+-1.3+-3.0 MeV. We interpret
these new states as the particles, the charmed-strange
analogs of the .Comment: 10 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
First Observation of B -> D(*) rho', rho' -> omega pi-
We report on the observation of B-> D(*) pi+ pi- pi- pi^o decays. The
branching ratios for D*+ and D*o are (1.72+/-0.14+/-0.24)% and
(1.80+/-0.24+/-0.27)%, respectively. Each final state has a D* omega pi-
component, with branching ratios (0.29+/-0.03+/-0.04)% and
(0.45+/-0.10+/-0.07)% for the D*+ and D*o modes, respectively. We also observe
B -> D omega pi- decays. The branching ratios for D+ and Do are
(0.28+/-0.05+/-0.04)% and (0.41+/-0.07+/-0.06)%, respectively. A spin parity
analysis of the D omega pi- final state prefers a wide 1^- resonance. A fit to
the omega pi- mass spectrum finds a central mass of (1349+/-25^{+10}_{-5}) MeV
and width of (547+/-86^{+46}_{-45}) MeV. We identify this object as the
rho(1450) or the \rho'.Comment: 42 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, To Appear in PR
Search for the Decay
We report on a search for the radiative decay U(1S) -> gamma + eta' in 61.3
pb^-1 of data taken with the CLEO II detector at the Cornell Electron Storage
Ring. Three decay chains were investigated, all involving eta' -> pi+ pi- +
eta, followed by eta -> gamma + gamma, eta -> pi0 + pi0 + pi0, or eta -> pi+ +
pi- + pi0. We find no candidate events in any of the three cases and set a
combined upper limit of 1.6 x 10^-5 at 90% C.L., significantly smaller than the
previous limit. We compare our result to other radiative U(1S) decays, to
radiative J/psi decays, and to theoretical predictions.Comment: 9 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to PR
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