Open Bottom Mesons Research Articles

Open bottom mesons in magnetized matter: Effects of (inverse) magnetic catalysis

In-medium masses of the pseudoscalar and vector open bottom mesons ([Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text], [Formula: see text]) are studied in the magnetized nuclear matter by considering the effects of Dirac sea, within the chiral effective model. The mass modifications arise due to the interactions of the open bottom mesons with the nucleons and the scalar mesons, calculated in terms of the scalar and number densities of the nucleons and the scalar fields fluctuations, within the chiral model. The effects of the magnetized Dirac sea lead to the considerable changes in the scalar fields with increasing magnetic field, which are related to the condensates of light quark–antiquark pairs. There is observed to be a (reduction) enhancement in the QCD light quark condensates with rising magnetic field, a phenomenon called (inverse) magnetic catalysis. The contribution of the magnetic field on the Fermi sea of nucleons is also taken into account through protons Landau energy levels and anomalous magnetic moments (AMMs) of the nucleons. The additional contribution of the lowest Landau level for the charged mesons is taken into account. In the presence of an external magnetic field, the spin–magnetic field interaction between the longitudinal component of the vector mesons and the pseudoscalar mesons ([Formula: see text], [Formula: see text] and [Formula: see text]) are studied, which lead to level repulsion between their masses with increasing magnetic field. The magnetic fields are observed to have significant contribution on the masses of the open bottom mesons through the Dirac sea effects taking into account the AMMs of nucleons. In vacuum, appreciable medium modifications are obtained due to the magnetized Dirac sea contribution with nonzero nucleonic AMMs.

Open bottom mesons and upsilon states in hot magnetized strange hadronic matter

The masses of open bottom mesons ([Formula: see text]([Formula: see text],[Formula: see text]), [Formula: see text]([Formula: see text],[Formula: see text]), [Formula: see text]([Formula: see text], [Formula: see text])) and upsilon states ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]) are investigated in the isospin asymmetric strange hadronic medium at finite temperature in the presence of strong magnetic fields using a chiral effective Lagrangian approach. Here the chiral SU(3) Lagrangian is generalized to include the bottom sector to incorporate the interactions of the open bottom mesons with the magnetized medium. At finite temperature, the number density and scalar density of baryons are expressed in terms of thermal distribution functions. For charged baryons, the magnetic field introduces contribution from Landau energy levels. The masses of the open bottom mesons get modified through their interactions with the baryons and the scalar mesons, which undergo modifications in a magnetized medium. The charged [Formula: see text], [Formula: see text] mesons have additional positive mass shifts due to Landau quantization in the presence of the magnetic field. The medium mass shift of the upsilon states originates from the modification of the gluon condensates simulated by the variation of dilaton field ([Formula: see text]) and a quark mass term in the magnetized medium. The open bottom mesons and upsilon states experience a mass drop in the magnetized medium. The masses of these mesons initially increase with a rise in temperature, and beyond a high value of temperature, their masses are observed to drop. When the temperature is below 90[Formula: see text]MeV, the in-medium masses of the mesons increase with an increase in the magnetic field. However, at high temperatures (T > 90 MeV), the masses are observed to drop with an increase in the magnetic field. These in-medium modifications can have observable effects in asymmetric heavy-ion collisions experiments.

Study of B, B_s mesons using heavy quark effective theory

Inspired by the lower statistical information in the bottom sector, in this paper, we calculate the masses and the strong decays of excited B and B_s mesons in the framework of heavy quark effective theory (HQET). Using an effective chiral Lagrangian approach based on heavy quark spin-flavor and light quark chiral symmetry, we explore the flavor independent parameters varDelta _F^{(c)} = varDelta _F^{(b)} and lambda _F^{(c)} = lambda _F^{(b)} to calculate the masses of experimentally unknown bottom mesons. Our predictions are consistent with the available experimental results and other theoretical studies. Their strong decay to the ground state bottom mesons plus light pseudoscalar mesons is calculated in terms of the square of the couplings g_H, g_S, g_T, g_X, g_Y, and g_R. The weighted average value of the couplings g_H, g_S and g_T is obtained in the charm sector (Phys. Rev. D 86: 054024, 2012) by fitting the calculated decay widths with experimental measurements, which will be used in the present study to analyze the strong decays of excited open bottom mesons. Moreover, the ratio of the decay rates is also predicted, which can be countered with future experimental data.

Upsilon decay widths in magnetized asymmetric nuclear matter

The in-medium partial decay widths of [Formula: see text] in magnetized asymmetric nuclear matter are studied using a field theoretic model for composite hadrons with quark (and antiquark) constituents. [Formula: see text] is the lowest bottomonium state which can decay to [Formula: see text] in vacuum. The medium modifications of the decay widths of [Formula: see text] to [Formula: see text] pair in magnetized matter arise due to the mass modifications of the decaying [Formula: see text] as well as of the produced [Formula: see text] and [Formula: see text] mesons. The in-medium masses of the open bottom meson in magnetized nuclear matter are computed from their interactions with the nucleons and the scalar mesons within a chiral effective model. The mass modification of the [Formula: see text] arises due to the medium modification of a scalar dilaton field, which is introduced in the model to simulate the gluon condensates of QCD. The effects of the anomalous magnetic moments for the proton and neutron are taken into consideration in the present investigation. The presence of the external magnetic field is observed to lead to different mass modifications within the [Formula: see text] as well as the [Formula: see text] doublets, even in isospin symmetric nuclear matter. This is due to the difference in the interactions of the proton and the neutron to the electromagnetic field. The charged [Formula: see text] mesons have additional contributions from the Landau energy levels, leading to positive shifts in their masses in the presence of a magnetic field. In the presence of an external magnetic field, there are contributions to the masses of the B, [Formula: see text] mesons and [Formula: see text] state (longitudinal component) due to the pseudoscalar meson–vector meson (PV) mixing ([Formula: see text], [Formula: see text] and [Formula: see text] mixings), which are also considered in this study. The PV mixing effects are observed to be the dominant contributions to the mass shifts of these mesons, which lead to appreciable modifications in the decay widths of [Formula: see text] to the neutral ([Formula: see text]) and the charged ([Formula: see text]) pairs in the presence of a magnetic field. These should have observable consequence in the production of open bottom mesons and bottomonium states at LHC and RHIC, where huge magnetic fields are produced in ultra-relativistic peripheral heavy-ion collisions.

Search for [formula omitted] tetraquark decays in 4 muons, B+B−, [formula omitted] and [formula omitted] channels at LHC

We perform a quantitative analysis of the bbb¯b¯ tetraquark decays into hidden- and open-bottom mesons and calculate, for the first time, the bbb¯b¯ tetraquark total decay width. On the basis of our results, we propose the bbb¯b¯→B+B−(B0B¯0)(Bs0B¯s0)→l+l−+X decays as the most suitable channels to observe the bbb¯b¯ tetraquark states, since the calculated two-lepton cross section upper limit, ≃39 fb, is so large as to be potentially detectable with the 2018 LHCb sensitivity, paving the way to the observation of the bbb¯b¯ tetraquark in the future LHCb upgrade. The 4μ signal for the ground state, JPC=0++, is likely to be too small even for the upgraded LHCb, but it may not be hopeless for the JPC=2++ fully-bottom state.

Open bottom mesons in asymmetric nuclear matter in the presence of strong magnetic fields

The modifications of the masses of the $B$ and $\bar B$ mesons in asymmetric nuclear matter in the presence of strong magnetic fields, are investigated using a chiral effective model. The medium modifications of these open bottom mesons arise due to their interactions with the scalar mesons and the nucleons. In the magnetized nuclear matter, the proton has contributions from the Landau levels. In the chiral effective model, the masses of the $B$ and $\bar B$ are calculated from the leading term, namely the vectorial Weinberg Tomozawa term as well as from the next to leading order contributions, i.e., due to the scalar exchange and the range terms. Due to the Weinberg-Tomozawa term, the $\bar B$ mesons experience an attractive interaction in the symmetric nuclear matter, whereas the $B$ mesons have a repulsive interaction. Inclusion of the contributions from the scalar exchange and the range terms as well, leads to drop of the masses of both $B$ and $\bar B$ mesons. The effect of the isospin asymmetry breaks the mass degeneracy of the $B^+$ and $B^0$ (as well as of the $B^-$ and $\bar {B^0}$) mesons, and its effect is observed to be large at high densities. The effects of anomalous magnetic moments of the nucleons are taken into account in the present study of the masses of the open bottom mesons in magnetized nuclear matter.

Open-flavor strong decays of open-charm and open-bottom mesons in the P03 model

We provide results for the open-flavor strong decays of open-charm ($D$ and $D_{\rm s}$) and open-bottom ($B$, $B_{\rm s}$ and $B_{\rm c}$) mesons. The decays are calculated in a modified version of the $^3P_0$ pair-creation model, assuming harmonic oscillator wave functions. The spectra of open-charm and open-bottom mesons used in the calculations are computed within Godfrey and Isgur's relativized quark model. Quantum number assignments are also provided. Our results are compared with the existing experimental data.

Decay widths of bottomonium states in matter: A field theoretic model for composite hadrons

We compute the in-medium partial decay widths of the bottomonium states to open bottom mesons ($B\bar B$) using a field theoretical model for composite hadrons with quark constituents. These decay widths are calculated by using the explicit constructions for the bottomonium states and the open bottom mesons ($B$ and $\bar B$), and, the quark antiquark pair creation term of the free Dirac Hamiltonian written in terms of the constituent quark field operators. These decay widths in the hadronic medium are calculated as arising from the mass modifications of the bottomonium states and the $B$ and $\bar B$ mesons, obtained in a chiral effective model. The decay amplitude in the present model is multiplied with a strength parameter for the light quark pair creation, which is fitted from the observed vacuum partial decay width of the bottomonium state, $\Upsilon (4S)$ to $B\bar B$. The effects of the isospin asymmetry, the strangeness fraction of the hadronic matter on the decay widths, arising due to the mass modifications due to these effects, have also been studied. There is observed to be appreciable effects from density, and the effects from isospin asymmetry on the parital decay widths of $\Upsilon \rightarrow B\bar B$ are observed to be quite pronounced at high densities. These effects should show up in the asymmetric heavy ion collisions in Compressed baryonic matter (CBM) experiments planned at the future facility at FAIR. The study of the $\Upsilon$ states will, however, require access to energies higher than the energy regime planned at the CBM experiment. The density effects on the decay widths of the bottomonium states should show up in the production of these states, as well as, in dilepton spectra at the Super Proton Synchrotron (SPS) energies.

Open bottom mesons in a hot asymmetric hadronic medium

The in-medium masses and optical potentials of $B$ and ${\bar B}$ mesons are studied in an isospin asymmetric, strange, hot and dense hadronic environment using a chiral effective model. The chiral $SU(3)$ model originally designed for the light quark sector, is generalized to include the heavy quark sector ($c$ and $b$) to derive the interactions of the $B$ and ${\bar B}$ mesons with the light hadrons. Due to large mass of bottom quark, we use only the empirical form of these interactions for the desired purpose, while treating the bottom degrees of freedom to be frozen in the medium. Hence, all medium effects are due to the in-medium interaction of the light quark content of these open-bottom mesons. Both $B$ and $\bar B$ mesons are found to experience net attractive interactions in the medium, leading to lowering of their masses in the medium. The mass degeneracy of particles and antiparticles, ($B^+$, $B^-$) as well as ($B^0$, $\bar {B^0}$), is observed to be broken in the medium, due to equal and opposite contributions from a vectorial Weinberg-Tomozawa interaction term. Addition of hyperons to the medium lowers further the in-medium mass for each of these four mesons, while a non-zero isospin asymmetry is observed to break the approximate mass degeneracy of each pair of isospin doublets. These medium effects are found to be strongly density dependent, and bear a considerably weaker temperature dependence. The results obtained in the present investigation are compared to predictions from the quark-meson coupling model, heavy meson effective theory, and the QCD Sum Rule approach.

Bottom-strange mesons in hyperonic matter

The in-medium behavior of bottom-strange pseudoscalar mesons in hot, isospin asymmetric and dense hadronic environment is studied using a chiral effective model. The same was recently generalized to the heavy quark sector and employed to study the behavior of open-charm and open-bottom mesons. The heavy quark (anti-quark) is treated as frozen and all medium modifications of these bottom-strange mesons are due to their strange anti-quark (quark) content. We observe a pronounced dependence of their medium mass on baryonic density and strangeness content of the medium. Certain aspects of these in-medium interactions are similar to those observed for the strange-charmed mesons in a preceding investigation, such as the lifting of mass-degeneracy of [Formula: see text] and [Formula: see text] mesons in hyperonic matter, while the same is respected in vacuum as well as in nuclear matter. In general, however, there is a remarkable distinction between the two species, even though the formalism predicts a completely analogous in-medium interaction Lagrangian density. We discuss in detail the reason for different in-medium behavior of these bottom-strange mesons as compared to charmed-strange mesons, despite the dynamics of the heavy quark being treated as frozen in both cases.