6,715 research outputs found
Muonium spectrum beyond the nonrelativistic limit
A generalization of the Gell-Mann-Low theorem is applied to the
antimuon-electron system. The bound state spectrum is extracted numerically. As
a result, fine and hyperfine structure are reproduced correctly near the
nonrelativistic limit (and for arbitrary masses). We compare the spectrum for
the relativistic value alpha = 0.3 with corresponding calculations in
light-front quantization.Comment: 6 pages, LaTeX, 2 figures, uses aipxfm.sty. Talk delivered at the XI
Mexican Workshop on Particles and Fields, Tuxtla Gutierrez, Mexico, November
7-12, 2007; to be published in the proceeding
Coherent nu-N scattering and the search for physics beyond the standard model
We focus in future proposals to measure coherent neutrino-nuclei scattering
and we show that such kind of experiments are very sensitive to nonstandard
neutrino interactions with quarks. First in a model independent parametrization
and then we focused in particular models such as leptoquarks and models with
extra neutral gauge bosons and with R-parity breaking interactions. We show
that in all these three different types of new physics it is possible to obtain
competitive bounds to those of future collider experiments. For the particular
case of leptoquarks we found that the expected sensitivity to the coupling and
mass for most of the future experimental setups is quite better than the
current constraints.Comment: 6 pages, 1 Figure, Talk given at 11th Mexican Workshop on Particles
and Fields 2007, Tuxtla Gutierrez, Mexico, 7-12 Nov 200
Neutrino Flavor States and the Quantum Theory of Neutrino Oscillations
The standard theory of neutrino oscillations is reviewed, highlighting the
main assumptions: the definition of the flavor states, the equal-momentum
assumption and the time = distance assumption. It is shown that the standard
flavor states are correct approximations of the states that describe neutrinos
in oscillation experiments. The equal-momentum assumption is shown to be
unnecessary for the derivation of the oscillation probability. The time =
distance assumption derives from the wave-packet character of the propagating
neutrinos. We present a simple quantum-mechanical wave-packet model which
allows us to describe the coherence and localization of neutrino oscillations.Comment: 16 pages; talk presented at the XI Mexican Workshop on Particles and
Fields, 7-12 November 2007, Tuxtla Gutierrez, Chiapas, Mexic
Constraining a bulk viscous matter-dominated cosmological model using SNe Ia, CMB and LSS
We present and constrain a cosmological model which component is a
pressureless fluid with bulk viscosity as an explanation for the present
accelerated expansion of the universe. We study the particular model of a
constant bulk viscosity coefficient \zeta_m. The possible values of \zeta_m are
constrained using the cosmological tests of SNe Ia Gold 2006 sample, the CMB
shift parameter R from the three-year WMAP observations, the Baryon Acoustic
Oscillation (BAO) peak A from the Sloan Digital Sky Survey (SDSS) and the
Second Law of Thermodynamics (SLT). It was found that this model is in
agreement with the SLT using only the SNe Ia test. However when the model is
submitted to the three cosmological tests together (SNe+CMB+BAO) the results
are: 1.- the model violates the SLT, 2.- predicts a value of H_0 \approx 53 km
sec^{-1} Mpc^{-1} for the Hubble constant, and 3.- we obtain a bad fit to data
with a \chi^2_{min} \approx 400 (\chi^2_{d.o.f.} \approx 2.2). These results
indicate that this model is ruled out by the observations.Comment: 4 pages, 1 figure. Work presented in the XI Mexican Workshop on
Particles and Fields, Tuxtla Gutierrez, Mexico, nov 7-12, 2007. Submitted to
AIP Conference Proceedings of this conferenc
Proton to pion ratio at RHIC from dynamical quark recombination
We propose an scenario to study, from a dynamical point of view, the thermal
recombination of quarks in the midsts of a relativistic heavy-ion collision. We
coin the term dynamical quark recombination to refer to the process of
quark-antiquark and three-quark clustering, to form mesons and baryons,
respectively, as a function of energy density. Using the string-flip model we
show that the probabilities to form such clusters differ. We apply these ideas
to the calculation of the proton and pion spectra in a Bjorken-like scenario
that incorporates the evolution of these probabilities with proper time and
compute the proton to pion ratio, comparing to recent RHIC data at the highest
energy. We show that for a standard choice of parameters, this ratio reaches
one, though the maximum is very sensitive to the initial evolution proper time.Comment: To appear in the proceedings of the XI Mexican Workshop on Particles
and Fields, Tuxtla Gutierrez Chiapas, Mexico, 7-12 Nov. 200
Nearly tri-bimaximal mixing in the S_3 flavour symmetry
We present an analysis of the theoretical neutrino mixing matrix,
V_{PMNS}^{th}, previously derived in the framework of the minimal S_3-invariant
extension of the Standard Model. All entries in the neutrino mixing matrix,
V_{PMNS}^{th}, the mixing angles and the Majorana phases are given as exact,
explicit analytical functions of the mass ratios of the charged leptons and
neutrinos, and one Dirac phase, in excellent agreement with the the latest
experimental data. Here, it will be shown that all entries in V_{PMNS}^{th} are
numerically very close to the tri-bimaximal form of the neutrino mixing matrix,
so that V_{PMNS}^{th} may be written as V^{tri}+\Delta V_{PMNS}^{tri}. The
small correction \Delta V_{PMNS}^{tri} is expressed as a sum of two terms:
first, a small correction term proportional to m_{e}/m_{\mu} depending only on
the charged lepton mass ratios and, second, a Cabbibo-like, small term, \delta
t_{12}, which is a function of both the charged lepton and the neutrino mass
ratios.Comment: 6 pages, Talk given at XI Mexican Workshop on Particles and Fields,
Tuxtla Gutierrez, Chiapas, Mexico, 7-12 Nov 2007. To be published in AIP
conference proceeding
Plan de marketing para el relanzamiento de Nomads Barbertrucks
Plan de Marketing para el relanzamiento de Nomads Barbertrucks” tiene como objetivo analizar la viabilidad del relanzamiento del negocio a partir de enero del 2022, luego de haber iniciado operaciones en agosto del 2020, durante la pandemia del COVID-19, con los objetivos de cumplir con sus obligaciones y cubrir sus costos, considerando las restricciones a nivel de afluencia, higiene y seguridad impuestas por el gobierno a consecuencia de la referida pandemia.
Nomads es una marca de barbería tipo clásica cuyo local se diferencia por ser un barbertruck, el cual se caracteriza por ser un módulo movible, con menores costos de implementación. Actualmente opera con 2 puntos de servicio, ambos en centros comerciales ubicados en Independencia. Para el relanzamiento, Nomads busca abrir dos puntos adicionales en los distritos de Chorrillos y Santa Anita. Todo punto será ubicado en centros comerciales, debido a su alta afluencia, consumo, y convenienci
Study of Zγ events and limits on anomalous ZZγ and Zγγ couplings in pp̄ collisions at s=1.96TeV
We present a measurement of the Zγ production cross section and limits on anomalous ZZγ and Zγγ couplings for form-factor scales of Λ=750 and 1000 GeV. The measurement is based on 138 (152) candidates in the eeγ (μμγ) final state using 320(290)pb-1 of pp̄ collisions at s=1.96TeV. The 95% C.L. limits on real and imaginary parts of individual anomalous couplings are |h10,30Z|<0.23, |h20,40Z|<0.020, |h10,30γ|<0.23, and |h20,40γ|<0.019 for Λ=1000GeV. © 2005 The American Physical Society
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