3,476 research outputs found
Spin and model identification of Z' bosons at the LHC
Heavy resonances appearing in the clean Drell-Yan channel may be the first
new physics to be observed at the proton-proton CERN LHC. If a new resonance is
discovered at the LHC as a peak in the dilepton invariant mass distribution,
the characterization of its spin and couplings will proceed via measuring
production rates and angular distributions of the decay products. We discuss
the discrimination of the spin-1 of Z' representative models (Z'_{SSM},
Z'_{psi}, Z'_{eta}, Z'_{chi}, Z'_{LR}, and Z'_{ALR}) against the
Randall-Sundrum graviton resonance (spin-2) and a spin-0 resonance (sneutrino)
with the same mass and producing the same number of events under the observed
peak. To assess the range of the Z' mass where the spin determination can be
performed to a given confidence level, we focus on the angular distributions of
the Drell-Yan leptons, in particular we use as a basic observable an
angular-integrated center-edge asymmetry, A_{CE}. The spin of a heavy Z' gauge
boson can be established with A_{CE} up to M_{Z'} \simeq 3.0 TeV, for an
integrated luminosity of 100 fb^{-1}, or minimal number of events around 110.
We also examine the distinguishability of the considered Z' models from one
another, once the spin-1 has been established, using the total dilepton
production cross section. With some assumption, one might be able to
distinguish among these Z' models at 95% C.L. up to M_{Z'} \simeq 2.1 TeV.Comment: 18 pages, 6 figure
Energy bands, conductance and thermoelectric power for ballistic electrons in a nanowire with spin-orbit interaction
We calculated the effects of spin-orbit interaction (SOI) on the energy
bands, ballistic conductance and the electron-diffusion thermoelectric power of
a nanowire by varying the temperature, electron density and width of the wire.
The potential barriers at the edges of the wire are assumed to be very high. A
consequence of the boundary conditions used in this model is determined by the
energy band structure, resulting in wider plateaus when the electron density is
increased due to larger energy-level separation as the higher subbands are
occupied by electrons. The nonlinear dependence of the transverse confinement
on position with respect to the well center excludes the "pole-like feature" in
the conductance which is obtained when a harmonic potential is employed for
confinement. At low temperature, the electron diffusion thermoelectric power
increases linearly with T but deviates from the linear behavior for large
values of T.Comment: Updated corrected version of the original submissio
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Determination of the hydrodynamic performance of marine propellers using fibre Bragg gratings
Downloading of the abstract is permitted for personal use only. A critical aspect in the design of marine propellers is their hydrodynamic performance which, when evaluated experimentally, requires a number of parameters to be monitored at the same time, i.e.The thrust and torque a propeller generates as well as the propeller shaft and vessel speed. In this investigation, three of those parameters are measured using Fibre Bragg Grating-based sensors, thus allowing for computationally derived performance values to be verified. For that purpose, open water tests were carried out where an instrumented propeller shaft was installed into a research vessel and measurements taken, evaluated and the results compared favorably with advanced computer-based simulations
Analytic Confinement and Regge Trajectories
A simple relativistic quantum field model with the Yukawa-type interaction is
considered to demonstrate that the analytic confinement of the constituent
("quarks") and carrier ("gluons") particles explains qualitatively the basic
dynamical properties of the spectrum of mesons considered as two-particle
stable bound states of quarks and gluons: the quarks and gluons are confined,
the glueballs represent bound states of massless gluons, the masses of mesons
are larger than the sum of the constituent quark masses and the Regge
trajectories of mesonic orbital excitations are almost linear.Comment: RevTeX, 16 pages, 3 figures and 2 table
Charmed quark component of the photon wave function
We determine the c-anti-c component of the photon wave function on the basis
of (i) the data on the transitions e+ e- -> J/psi(3096), psi(3686), psi(4040),
psi(4415), (ii) partial widths of the two-photon decays eta_{c0}(2979),
chi_{c0}(3415), chi_{c2}(3556) -> gamma-gamma, and (iii) wave functions of the
charmonium states obtained by solving the Bethe-Salpeter equation for the
c-anti-c system. Using the obtained c-anti-c component of the photon wave
function we calculate the gamma-gamma decay partial widths for radial
excitation 2S state, eta_{c0}(3594) -> gamma-gamma, and 2P states
chi_{c0}(3849), chi_{c2}(3950) -> gamma-gamma.Comment: 20 pages, 8 figure
Relativistic quantum model of confinement and the current quark masses
We consider a relativistic quantum model of confined massive spinning quarks
and antiquarks which describes leading Regge trajectories of mesons. The quarks
are described by the Dirac equations and the gluon contribution is approximated
by the Nambu-Goto straight-line string. The string tension and the current
quark masses are the main parameters of the model. Additional parameters are
phenomenological constants which approximate nonstring short-range
contributions. Comparison of the measured meson masses with the model
predictions allows one to determine the current quark masses (in MeV) to be
. The chiral
model[23] makes it possible to estimate from here the - and -quark masses
to be ~ Mev and Mev.Comment: 15 pages, LATEX, 2 tables. (submitted to Phys.Rev.D
Lattice thermal conductivity of pristine and doped (B,N) Graphene
In this paper, the effect of B and N doping on the phonon induced thermal
conductivity of graphene has been investigated. This study is important when
one has to evaluate the usefulness of electronic properties of B and N doped
graphene. We have performed the calculations by employing density functional
perturbation theory(DFPT) to calculate the inter-atomic forces=force constants
of pristine/doped graphene. Thermal conductivity calculations have been carried
out by making use of linearized Boltzmann transport equations (LBTE) under
single-mode relaxation time approximation (RTA). The thermal conductivity of
pristine graphene has been found to be of the order of 4000W/mK at 100K, which
decreases gradually with an increase in temperature. The thermal conductivity
decreases drastically by 96 % to 190 W/mK when doped with 12.5 % B and reduces
by 99 % to 30 W/mK with 25 % B doping. When graphene is doped with N, the
thermal conductivity decreases to 4 W/mK and 55 W/mK for 12.5 % and 25 % doping
concentration, respectively. We have found that the thermal conductivity of
doped graphene show less sensitivity to change in temperature. It has also been
shown that the thermal conductivity of graphene can be tuned with doping and
has a strong dependence on doping concentration.Comment: Accepted for publication in Material Research Expres
Quark--antiquark states and their radiative transitions in terms of the spectral integral equation. {\Huge II.} Charmonia
In the precedent paper of the authors (hep-ph/0510410), the states
were treated in the framework of the spectral integral equation, together with
simultaneous calculations of radiative decays of the considered bottomonia. In
the present paper, such a study is carried out for the charmonium
states. We reconstruct the interaction in the -sector on the basis of
data for the charmonium levels with , , ,
, , and radiative transitions
, , ,
and , ,
. The levels and their wave functions
are calculated for the radial excitations with . Also, we determine the
component of the photon wave function using the annihilation
data: , , , , , and perform the calculations of the partial widths of
the two-photon decays for the states: , ,
, and states:
, , . We discuss the status of the recently observed states
X(3872) and Y(3941): according to our results, the X(3872) can be either
or , while Y(3941) is .Comment: 24 pages, 9 figure
Interplay of quark and meson degrees of freedom in a near-threshold resonance
We investigate the interplay of quark and meson degrees of freedom in a
physical state representing a near-threshold resonance for the case of a single
continuum channel. We demonstrate that such a near-threshold resonance may
possess quite peculiar properties if both quark and meson dynamics generate
weakly coupled near-threshold poles in the S-matrix. In particular, the
scattering t-matrix may possess zeros in this case. We also discuss possible
implications for production reactions as well as studies within lattice QCD.Comment: LaTeX2e, 11 pages, minor typo corrections, to appear in Eur.Phys.J.
Spin identification of the Randall-Sundrum resonance in lepton-pair production at the LHC
The determination of the spin of the quantum states exchanged in the various
non-standard interactions is a relevant aspect in the identification of the
corresponding scenarios. We discuss the identification reach at LHC on the
spin-2 of the lowest-lying Randall-Sundrum resonance, predicted by gravity with
one warped extra dimension, against spin-1 and spin-0 non-standard exchanges
with the same mass and producing the same number of events in the cross
section. We focus on the angular distributions of leptons produced in the
Drell-Yan process at the LHC, in particular we use as basic observable a
normalized integrated angular asymmetry A_{CE}. Our finding is that the 95%
C.L. identification reach on the spin-2 of the RS resonance (equivalently, the
exclusion reach on both the spin-1 and spin-0 hypotheses for the peak) is up to
a resonance mass scale of the order of 1.0 or 1.6 TeV in the case of weak
coupling between graviton excitations and SM particles (k/{\bar M}_{Pl}=0.01)
and 2.4 or 3.2 TeV for larger coupling constant (k/{\bar M}_{Pl}=0.1) for a
time-integrated LHC luminosity of 10 or 100 fb^{-1}, respectively. Also, some
comments are given on the complementary r\^oles of the angular analysis and the
eventual discovery of the predicted second graviton excitation in the
identification of the RS scenario.Comment: 27 pages, 11 figures. v2: References added, clarifications; version
to appear in PR
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