Search results for "Spectral"
showing 10 items of 3116 documents
Quarkonium spectral functions with complex potential
2011
Abstract We study quarkonium spectral functions at high temperatures using a potential model with complex potential. The real part of the potential is constrained by the lattice QCD data on static quark anti-quark correlation functions, while the imaginary part of the potential is taken from perturbative calculations. We find that the imaginary part of the potential has significant effect on quarkonium spectral functions, in particular, it leads to the dissolution of the 1S charmonium and excited bottomonium states at temperatures about 250 MeV and melting of the ground state bottomonium at temperatures slightly above 450 MeV.
Prospects of Medium Tomography using 2-,3- and 4-Particle Correlations for a (semi-)hard Trigger
2007
Hard partons propagating through hot and dense matter lose energy, leading to the observed depletion of hard hadron spectra in nucleus nucleus collision as compared to scaled proton proton collisions. This lost energy has to be redistributed in the medium due to the conservation of energy, which is manifest in the p_T dependence of the angular correlation pattern of hadrons associate with a (semi-) hard trigger. While at low p_T a splitting of a broad peak is observed, at high p_T the structure shows vacuum width, albeit with reduced yield. This sugests a transfer of energy from hard partons to a collectively recoiling medium. We present a systematic study of these phenomena using a realist…
Understanding the Low Energy Hadron Spectrum in a Chiral Quark Cluster Model
1999
The low energy N and Δ spectra are studied by means of a chiral quark cluster model. We solve the Schrodinger equation in the hyperspherical harmonic approach. The interacting potential includes Goldstone boson exchanges besides the usual one-gluon exchange. The predicted baryonic spectrum is quite reasonable. However, if consistency with the two-baryon sector is required, the observed inversion of the positive and negative parity excitations of the nucleon cannot be obtained. Alternative solutions are discussed.
Quark-model study of few-baryon systems
2005
We review the application of non-relativistic constituent quark models to study one, two and three non-strange baryon systems. We present results for the baryon spectra, potentials and observables of the NN, N$\Delta$, $\Delta\Delta$ and NN$^*(1440)$ systems, and also for the binding energies of three non-strange baryon systems. We make emphasis on observable effects related to quark antisymmetry and its interplay with quark dynamics.
Exclusive semileptonic heavy meson decays including lepton mass effects
1990
We discuss the exclusive semi-leptonic (s.l.) bottom meson decaysB→D(D*)+l+v where we include non-zero lepton mass effects in the kinematics and dynamics. We develop the general formalism for the non-zero lepton mass case. We then look at how rates, spectra and angular correlations are affected by non-zero lepton masses in the context of a specific spectator quark model. Numerical results are presented for s.l. decays involving thee-, μ- and τ-leptons. We also discuss the s.l. decaysB→π(ρ),D→K(K*) and the free quark decay model.
Taming the higher power corrections in semileptonic B decays
2016
We study the effect of dimension 7 and 8 operators on inclusive semileptonic B decays and the extraction of |Vcb|. Using moments of semileptonic B decay spectra and information based on the Lowest-Lying State saturation Approximation (LLSA) we perform a global fit of the nonperturbative parameters of the heavy quark expansion including for the first time the O(1/mb^{4,5}) contributions. Higher power corrections appear to have a very small effect on the extraction of |Vcb|, independently of the weight we attribute to the LLSA.
Recurrence of the blue wing enhancements in the high ionization lines of SDSS 1004+4112 A
2006
We present integral field spectroscopic observations of the quadruple-lensed QSO SDSS 1004+4112 taken with the fiber system INTEGRAL at the William Herschel Telescope on 2004 January 19. In 2003 May, a blueward enhancement in the high-ionization lines of SDSS 1004+4112A was detected, and then it faded. Our observations are the first to note a second event of similar characteristics less than 1 year after. Although initially attributed to microlensing, the resemblance among the spectra of both events and the absence of microlensing-induced changes in the continuum of component A are puzzling. The lack of a convincing explanation under the microlensing or intrinsic variability hypotheses make…
Scattering of Particles by Potentials
2013
The three prototypes of spectra of self-adjoint operators, the discrete spectrum, with or without degeneracy, the continuous spectrum, and the mixed spectrum, as well as the corresponding wave functions, contain important information about the physical systems that they describe
Photometric and Hα Observations of LSI+61°303
1994
The Be massive X-ray binary LSI+61°303 is a 26.5 days periodic radiosource (Taylor & Gregory, 1984), exhibiting radio outbursts maxima between phases 0.6-0.8. Evidence of a photometric period of similar value has also been reported (Paredes & Figueras, 1986; Mendelson & Mazeh, 1989). The previous spectroscopic radial velocity observations of Hutchings & Crampton (1981) are in agreement with the radio period, and give support to the presence of a companion. We present new optical and infrared photometric observations and high resolution Hα spectra of LSI+61°303.
A detailed spectroscopy of the carbon-rich star BD +57° 2161
2005
An LTE abundance analysis based on high-resolution spectra is presented for the carbon-rich star BD +57° 2161, whose evolutionary status is unknown. With [C/Fe] = +0.4 dex and a mean s-process overabundance of [s/Fe] ≃ +1.5 dex the peculiar atmospheric composition of BD +57° 2161 is confirmed. The 12 C/ 13 C abundance ratio was found to be about 10. The mild iron deficiency, [Fe/H] = -0.2, supports the idea that BD +57° 2161 could be an old-disk-population object. Radial-velocity measurements confirm the binary nature of the star. Therefore the peculiar chemical composition could be due to the mass transfer from the secondary - AGB star in the past. Orbital parameters are estimated for anot…