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C. Albertus

Publications and source records attributed to C. Albertus.

At least 37 records · Page 2Linked to original sources
arXiv2014

Angular distribution in two-particle emission induced by neutrinos and electrons

The angular distribution of the phase space arising in two-particle emission reactions induced by electrons and neutrinos is computed in the laboratory (Lab) system by boosting the isotropic distribution in the center of mass (CM) system used in Monte Carlo generators. The Lab distribution has a singularity for some angular values, coming from the Jacobian of the angular transformation between CM and Lab systems. We recover the formula we obtained in a previous calculation for the Lab angular distribution. This is in accordance with the Monte Carlo method used to generate two-particle events for neutrino scattering\cite{Sob12}. Inversely, by performing the transformation to the CM system, it can be shown that the phase-space function, which is proportional to the two particle-two hole (2p-2h) hadronic tensor for a constant current operator, can be computed analytically in the frozen nucleon approximation, if Pauli blocking is absent. The results in the CM frame confirm our previous work done using an alternative approach in the Lab frame. The possibilities of using this method to compute the hadronic tensor by a boost to the CM system are analyzed.

nucl-th↗
arXiv2014

Relativistic effects in two-particle emission for electron and neutrino reactions

Two-particle two-hole contributions to electroweak response functions are computed in a fully relativistic Fermi gas, assuming that the electroweak current matrix elements are independent of the kinematics. We analyze the genuine kinematical and relativistic effects before including a realistic meson-exchange current (MEC) operator. This allows one to study the mathematical properties of the non-trivial seven-dimensional integrals appearing in the calculation and to design an optimal numerical procedure to reduce the computation time. This is required for practical applications to CC neutrino scattering experiments, where an additional integral over the neutrino flux is performed. Finally we examine the viability of this model to compute the electroweak 2p-2h response functions.

nucl-th↗
arXiv2014

$B_s$ mesons: semileptonic and nonleptonic decays

In this contribution we compute some nonleptonic and semileptonic decay widths of $B_s$ mesons, working in the context of constituent quark models \cite{Albertus:2014gba, Albertus:2014bfa}. For the case of semileptonic decays we consider reactions leading to kaons or different $J^π$ $D_s$ mesons. The study of nonleptonic decays has been done in the factorisation approximation and includes the final states enclosed in Table 2.

hep-ph↗
arXiv2014

$\bar B_s\to K$ semileptonic decay from an Omnès improved nonrelativistic quark model

We study the $f^+$ form factor for the $\bar B_s\to K^+\ell^-\barν_\ell$ semileptonic decay in a nonrelativistic quark model. The valence quark contribution is supplemented with a $\bar B^*$-pole term that dominates the high $q^2$ region. To extend the quark model predictions from its region of applicability near $q^2_{\rm max}=(M_{B_s}-M_K)^2$, we use a multiply-subtracted Omnès dispersion relation. We fit the subtraction constants to a combined input from previous light cone sum rule results in the low $q^2$ region and the quark model results (valence plus $\bar B^*$-pole) in the high $q^2$ region. From this analysis, we obtain $Γ(\bar B_s\to K^+\ell^-\barν_\ell)=(5.47^{+0.54}_{-0.46})|V_{ub}|^2\times 10^{-9}\,{\rm MeV}$, which is about 10% and 20% higher than predictions based on Lattice QCD and QCD light cone sum rules respectively.

hep-ph↗
arXiv2014

The Large Observatory For x-ray Timing

The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final down-selection for a launch slot in 2022-2024. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument, LOFT will study the behaviour of matter under extreme conditions, such as the strong gravitational field in the innermost regions of accretion flows close to black holes and neutron stars, and the supra-nuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m 2 effective area, 2-30 keV, 240 eV spectral resolution, 1 deg collimated field of view) and a WideField Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g. GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the status of the mission at the end of its Phase A study.

astro-ph.IM↗
arXiv2014

$\bar B_s\to K$ semileptonic decay from an Omnès improved constituent quark model

We study the $f^+$ form factor for the semileptonic $\bar B_s\to K^+\ell^-\barν_\ell$ decay in a constituent quark model. The valence quark estimate is supplemented with the contribution from the $\bar B^*$ pole that dominates the high $q^2$ region. We use a multiply-subtracted Omnès dispersion relation to extend the quark model predictions from its region of applicability near $q^2_{\rm max}=(M_{B_s}-M_K)^2\sim 23.75$ GeV$^2$ to all $q^2$ values accessible in the physical decay. To better constrain the dependence of $f^+$ on $q^2$, we fit the subtraction constants to a combined input from previous light cone sum rule [Phys. Rev. D 78 (2008) 054015] and the present quark model results. From this analysis, we obtain $Γ(\bar B_s\to K^+\ell^-\barν_\ell)=(5.45^{+0.83}_{-0.80})|V_{ub}|^2\times 10^{-9}\,{\rm MeV}$, which is about 20\% higher than the prediction based only on QCD light cone sum rule estimates. Differences are much larger for the $f^+$ form factor in the region above $q^2=15$ GeV$^2$.

hep-ph↗
arXiv2014

Semileptonic and nonleptonic decays of $B_s$ mesons

We investigate the semileptonic and nonleptonic decays of $B_s$ mesons. We work within the context of nonrelativistic constituent quark models. We calculate the different form factors that parameterize the hadron matrix elements.

hep-ph↗
arXiv2014

Weak decays of $\bar B_s$ mesons

In the present work we study the semileptonic decays of $\bar B_s$ mesons in the context of nonrelativistic constituent quark models. We estimate the uncertainties of our calculation using different interquark potentials to obtain the meson wave functions. We check the results from our model against the predictions of Heavy Quark Symmetry, in the limit of infinite heavy quark mass. We also study the nonleptonic decays of $\bar B_s$ mesons within the factorization approximation.

hep-ph↗
arXiv2013

Exclusive $c \to s,d$ semileptonic decays of spin-1/2 and spin-3/2 $cb$ baryons

We present results for exclusive semileptonic decay widths of ground state spin-$1/2$ and spin-$3/2$ $cb$ baryons corresponding to a $c\to s, d$ transition at the quark level. The relevance of hyperfine mixing in spin-1/2 $cb$ baryons is shown. Our form factors are compatible with heavy quark spin symmetry constraints obtained in the infinite heavy quark mass limit.

hep-ph↗
arXiv2013

$ΛΛ$ interaction and hypernuclei

Data on $ΛΛ$ hypernuclei provide a unique method to learn details about the strangeness S =- 2 sector of the baryon-baryon interaction. From the free space Bonn-Jülich potentials, determined from data on baryon-baryon scattering in the S = 0, -1 channels, we construct an interaction in the S =-2 sector to describe the experimentally known LL hypernuclei. After including short-range (Jastrow) and RPA correlations, we find masses for these LL hypernuclei in a reasonable agreement with data, taking into account theoretical and experimental uncertainties. Thus, we provide a natural extension, at low energies, of the Bonn-Jülich one-boson exchange potentials to the S =-2 channel.

nucl-th↗
arXiv2013

A nonrelativistic quark model evaluation of exclusive $b\to c$ semileptonic decay of triply heavy baryons and $c\to s,d$ semileptonic decay of $cb$ baryons

We present results for exclusive $b\to c$ semileptonic decays of ground state triply-heavy baryons and for semileptonic $c\to s,d$ decays of doubly heavy ground state $cb$ baryons. In both cases, we have derived for the first time heavy quark spin symmetry relations for the hadronic amplitudes near zero recoil. Though strictly valid in the limit of very large heavy quark masses and near zero recoil, they turn out to be reasonable accurate for the whole available phase space in these decays and for the actual heavy quark masses we use. With these relations we have made approximate, but model independent, predictions for ratios of decay widths. In the case of spin-1/2 $cb$ baryons, we find that hyperfine mixing in the wave function has a great impact on their $c\to s,d$ decay widths.

hep-ph↗
arXiv2012

Semileptonic decays of spin-1/2 doubly charmed baryons

We evaluate exclusive semileptonic decays of ground-state spin-1/2 doubly heavy charmed baryons. The decays are driven by a $c\to s,d$ transition at the quark level. Our form factors are consistent with Heavy Quark Symmetry constraints. The latter are valid in the limit of infinitely heavy quark mass at zero recoil.

hep-ph↗
arXiv2012

Exclusive $c\to s,d$ semileptonic decays of ground-state spin-1/2 and spin-3/2 doubly heavy $cb$ baryons

We evaluate exclusive semileptonic decays of ground-state spin-1/2 and spin-3/2 doubly heavy $cb$ baryons driven by a $c\to s,d$ transition at the quark level. We check our results for the form factors against heavy quark spin symmetry constraints obtained in the limit of very large heavy quark masses and near zero recoil. Based on those constraints we make model independent, though approximate, predictions for ratios of decay widths.

hep-ph↗
arXiv2012

Nonleptonic $B \to D^{(*)}D_{sJ}^{(*)}$ decays and the nature of the orbitally excited charmed-strange mesons

The Belle Collaboration has recently reported a study of the decays $B \to D_{s1}(2536)^{+}\bar{D}^{(\ast)}$ and has given also estimates of relevant ratios between branching fractions of decays $B \to D^{(\ast)}D_{sJ}^{(\ast)}$ providing important information to check the structure of the $D_{s0}^{\ast}(2317)$, $D_{s1}(2460)$ and $D_{s1}(2536)$ mesons. The disagreement between experimental data and Heavy Quark Symmetry has been used as an indication that $D_{s0}^{\ast}(2317)$ and $D_{s1}(2460)$ mesons could have a more complex structure than the canonical $c\bar{s}$ one. We analyze these ratios within the framework of a constituent quark model, which allows us to incorporate the effects given by finite $c$-quark mass corrections. Our findings are that while the $D_{s1}(2460)$ meson could have a sizable non-$q\bar{q}$ component, the $D_{s0}^{\ast}(2317)$ and $D_{s1}(2536)$ mesons seem to be well described by a pure $q\bar{q}$ structure.

hep-ph↗
arXiv2011

Semileptonic $B$ and $B_{s}$ decays into orbitally excited charmed mesons

The BaBar Collaboration has recently reported products of branching fractions that include $B$ meson semileptonic decays into final states with charged and neutral $D_{1}(2420)$ and $D_{2}^{\ast}(2460)$, two narrow orbitally excited charmed mesons. We evaluate these branching fractions, together with those concerning $D_{0}^{\ast}(2400)$ and $D_{1}'(2430)$ mesons, within the framework of a constituent quark model. The calculation is performed in two steps, one of which involves a semileptonic decay and the other is mediated by a strong process. Our results are in agreement with the experimental data. We also extend the study to semileptonic decays of $B_{s}$ into orbitally excited charmed-strange mesons, providing predictions to the possible measurements to be carried out at LHC.

hep-ph↗
arXiv2011

Exclusive $c\to s,d$ semileptonic decays of ground-state spin-1/2 doubly charmed baryons

We evaluate exclusive semileptonic decays of ground-state spin-1/2 doubly heavy charmed baryons driven by a $c\to s,d$ transition at the quark level. Our results for the form factors are consistent with heavy quark spin symmetry constraints which are valid in the limit of an infinitely massive charm quark and near zero recoil. Only a few exclusive semileptonic decay channels have been theoretically analyzed before. For those cases we find that our results are in a reasonable agreement with previous calculations.

hep-ph↗