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D. R. Entem

Publications and source records attributed to D. R. Entem.

At least 55 records · Page 3Linked to original sources
arXiv2012

Scaling of the 3P0 strength in heavy meson strong decays

The phenomenological 3P0 decay model has been extensively applied to calculate meson strong decays. The strength γ of the decay interaction is regarded as a free flavor independent constant and is fitted to the data. We calculate through the 3P0 model the total strong decay widths of the mesons which belong to charmed, charmed-strange, hidden charm and hidden bottom sectors. The wave function of the mesons involved in the strong decays are given by a constituent quark model that describes well the meson phenomenology from the light to the heavy quark sector. A global fit of the experimental data shows that, contrarily to the usual wisdom, the γ depends on the reduced mass of the quark-antiquark pair in the decaying meson. With this scale-dependent strength γ, we are able to predict the decay width of orbitally excited B mesons not included in the fit.

hep-ph↗
arXiv2012

Molecular structures in charmonium spectrum: The $XYZ$ puzzle

We study in the framework of a constituent quark model the possible contributions of molecular structures to the XYZ charmonium like states. We analyze simultaneously the $c\bar{c}$ structures and the possible molecular components in a formalism which allows us to treat channels below and above thresholds. The only molecular state found in the $1^{++}$ sector correspond to the X(3872). Molecular resonances also appear with other quantum numbers. So, the so called Y(3940) and the X(3915) are suggested to be $J^{PC}=0^{++}$ charmonium states. In the $J^{PC}=1^{--}$ sector we also found significant contributions of the molecular structures which can affect the phenomenology.

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

Molecular effects in Charmonium Spectrum

We study the influence of possible molecular structures in the charmonium spectrum. We focus on the $0^{++}$ and $1^{--}$ sectors. In the first one we coupled the $2 ^3P_0$ $q\bar q$ pair with $DD$, $J/ψω$, $D_sD_s$ and $J/ψϕ$ channels and we obtain two states compatibles with the X(3945) and the Y(3940). In the second one we include the $3^3S_1$ and $2^3D_1$ charmonium states coupled to $DD$, $DD^*$, $D^*D^*$, $D_sD_s$, $D_sD_s^*$ and $D_s^*D_s^*$. In this calculation we obtain a new molecular state that could be the G(3900) or the controversial Y(4008) and two $c\bar c$ states dressed by the molecular components assigned to the $ψ(4040)$ and the $ψ(4160)$. The two $c\bar c$ states show interesting properties and in particular they solve the strong disagreement of the decay branching ratios measured by BABAR.

hep-ph↗
arXiv2011

Renormalization approach to constituent quark models of Quarkonium

Constituent quark models, while successful, require a great deal of fine tuning of the short distance interactions by introducing phenomenological gluonic form factors which are ultimately designed to accurately reproduce the spectrum. We apply and develop renormalization ideas to reduce the short distance sensitivity and show that, as naively expected, but not explicitly implemented in the models, the physics of binding is entirely linked to the string tension whereas leptonic decays depend more on the gluon exchange potential. We also show how the spectrum of S- and D- $1^{--}$ states is successfully intertwined through the singular tensor interaction.

hep-ph↗
arXiv2011

Chiral effective field theory and nuclear forces

We review how nuclear forces emerge from low-energy QCD via chiral effective field theory. The presentation is accessible to the non-specialist. At the same time, we also provide considerable detailed information (mostly in appendices) for the benefit of researchers who wish to start working in this field.

nucl-th↗
arXiv2010

Coupled channel approach to the structure of the X(3872)

We have performed a coupled channel calculation of the $1^{++}$ $c\bar c$ sector including $q\bar q$ and $DD^*$ molecular configurations. The calculation was done within a constituent quark model which successfully describes the meson spectrum, in particular the $c\bar c$ $1^{--}$ sector. Two and four quark configurations are coupled using the $^3P_0$ model. The elusive X(3872) meson appears as a new state with a high probability for the $DD^*$ molecular component. When the mass difference between neutral and charged states is included a large $D^0 {D^*}^0$ component is found which dominates for large distances and breaks isospin symmetry in the physical state. The original $c\bar c(2 ^3P_1)$ state acquires a sizable $DD^*$ component and can be identified with the X(3940). We study the $B\to K π^+ π^-J/ψ$ and $B\to K D^0 D^{*0}$ decays finding a good agreement with Belle and BaBar experimental data.

hep-ph↗
arXiv2010

The X(3872) and other possible $XYZ$ molecular states

We perform a coupled channel calculation of the $DD^*$ and $c\bar c$ sectors in the framework of a constituent quark model. The interaction for the $DD^*$ states is obtained using the Resonant Group Method (RGM) and the underlying quark interaction model. The coupling with the two quark system is performed using the $^3 P_0$ model. The X(3872) is found as a molecular state with a sizable $c\bar c$ component. A comparison with Belle and BaBar data has been done, finding a good agreement. Other possible molecular molecular states are discussed.

hep-ph↗
arXiv2010

Renormalization of the leading-order chiral nucleon-nucleon interaction and bulk properties of nuclear matter

We renormalize the two-nucleon interaction at leading order (LO) in chiral perturbation theory using the scheme proposed by Nogga, Timmermans, and van Kolck--also known as modified Weinberg counting. With this interaction, we calculate the energy per nucleon of symmetric nuclear matter in the Brueckner pair approximation and obtain a converged, cutoff-independent result that shows saturation, but also substantial underbinding. We find that the renormalized LO interaction is characterized by an extraordinarily strong tensor force (from one-pion exchange), which is the major cause for the lack of binding. The huge tensor force also leads to the unusually large wound integral of 40% in nuclear matter, which implies a very slow convergence of the hole-line or coupled-cluster expansion, rendering this interaction impractical for many-body calculations. In view of the unusual properties of the renormalized LO interaction and in view of the poor convergence of the nuclear many-body problem with this interaction, there is doubt if this interaction and its predictions can serve as a reasonable and efficient starting point that is improved by perturbative corrections.

nucl-th↗
arXiv2010

Nuclear forces from chiral EFT: The unfinished business

In spite of the great progress we have seen in recent years in the derivation of nuclear forces from chiral effective field theory (EFT), some important issues are still unresolved. In this contribution, we discuss the open problems which have particular relevance for microscopic nuclear structure, namely, the proper renormalization of chiral nuclear potentials and sub-leading many-body forces.

nucl-th↗
arXiv2009

Renormalization of the Off-shell chiral two-pion exchange NN interactions

The renormalization, finiteness and off-shellness of short distance power like singular interactions is discussed. We show analytically that the renormalizability of the off-shell scattering amplitude relies completely on the corresponding on-shell amplitude without proliferation of new counterterms. We illustrate the result by complementary calculations both in coordinate as well as in momentum space in the simplest 1S0 channel for chiral np interactions including Two Pion Exchange.

nucl-th↗
arXiv2008

Charm spectroscopy beyond the constituent quark model

We study the nature of the new charm and charmonium like states observed in the last few years, using a constituent quark model with an screened confinement potential. In the open charm sector we discuss different options for the $D_{sJ}(2860)$ including tetraquark configurations. In the hidden charm sector the new Y(4360) and Y(4660) are interpreted as $1^{--}$ states. The influence in the puzzling 3940 MeV region of multiquark configuration is discussed.

hep-ph↗
arXiv2008

Renormalization of chiral two-pion exchange NN interactions. Momentum vs. coordinate space

The renormalization of the chiral np interaction in the 1S0 channel to N3LO in Weinberg counting for the long distance potential with one single momentum and energy independent counterterm is carried out. This renormalization scheme yields finite and unique results and is free of short distance off-shell ambiguities. We observe good convergence in the entire elastic range below pion production threshold and find that there are some small physical effects missing in the purely pionic chiral NN potential with or without inclusion of explicit Delta degrees of freedom. We also study the renormalizability of the standard Weinberg counting at NLO and N2LO when a momentum dependent polynomial counterterm is included. Our numerical results suggest that the inclusion of this counterterm does not yield a convergent amplitude (at NLO and N2LO).

nucl-th↗
arXiv2007

Low Momentum Nucleon-Nucleon Interactions and Shell-Model Calculations

In the last few years, the low-momentum nucleon-nucleon (NN) interaction V-low-k derived from free-space NN potentials has been successfully used in shell-model calculations. V-low-k is a smooth potential which preserves the deuteron binding energy as well as the half-on-shell T-matrix of the original NN potential up to a momentum cutoff Lambda. In this paper we put to the test a new low-momentum NN potential derived from chiral perturbation theory at next-to-next-to-next-to-leading order with a sharp low-momentum cutoff at 2.1 fm-1. Shell-model calculations for the oxygen isotopes using effective hamiltonians derived from both types of low-momentum potential are performed. We find that the two potentials show the same perturbative behavior and yield very similar results.

nucl-th↗
arXiv2005

Towards a consistent approach to nuclear structure: EFT of two- and many-body forces

We review the nuclear forces currently in use, i.e., the high-precision NN potentials of the 1990's and the nuclear two- and many-body forces based upon chiral effective field theory (EFT). We argue that the EFT approach is superior to any of the older schemes. Since accurate chiral forces are available now, the stage is set for microscopic nuclear structure to move into a new exciting era.

nucl-th↗