Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We describe predictions for top quark pair differential distributions at hadron colliders, by combining the next-to-next-to-leading order quantum chromodynamics calculations and next-to-leading order electroweak corrections with double resummation at the next-to-next-to-leading logarithmic accuracy of threshold logarithms and small-mass logarithms. To the best of our knowledge, this is the first study to present such a combination, which incorporates all known perturbative information. Numerical results are presented for the invariant-mass distribution, transverse-momentum distribution, and rapidity distributions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the tensor form factors of <jats:inline-formula> <jats:tex-math><?CDATA $ P\to P,\,S,\,V $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083105_M2.jpg" xlink:type="simple" /> </jats:inline-formula>, and <jats:italic>A</jats:italic> transitions within the standard light-front (SLF) and the covariant light-front (CLF) quark models (QMs). The self-consistency and Lorentz covariance of CLF QM are analyzed via these quantities, and the effects of zero-mode are discussed. For the <jats:inline-formula> <jats:tex-math><?CDATA $ P\to V $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083105_M3.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:italic>A</jats:italic> transitions, besides the inconsistency between the results extracted via longitudinal and transverse polarization states, which is caused by the residual <jats:inline-formula> <jats:tex-math><?CDATA $ \omega $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083105_M4.jpg" xlink:type="simple" /> </jats:inline-formula>-dependent spurious contributions, we find and analyze a “novel” self-consistence problem of the traditional CLF QM, caused by different strategies for dealing with the trace term in CLF matrix element. A possible solution to the problems of traditional CLF QM is discussed and confirmed numerically. Finally, the theoretical predictions for the tensor form factors of some <jats:inline-formula> <jats:tex-math><?CDATA $ c\to q,\,s $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083105_M5.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ b\to q,\,s\,,c $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083105_M6.jpg" xlink:type="simple" /> </jats:inline-formula> ( <jats:inline-formula> <jats:tex-math><?CDATA $ q = u,d $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083105_M7.jpg" xlink:type="simple" /> </jats:inline-formula>) induced <jats:inline-formula> <jats:tex-math><?CDATA $ P\to P,\,S,\,V $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083105_M8.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:italic>A</jats:italic> transitions are updated within the CLF QM with a self-consistent scheme. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the phase transition between the pion condensed phase and normal phase, as well as chiral phase transition in a two flavor ( <jats:inline-formula> <jats:tex-math><?CDATA ${\cal{N}}_f=2$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083106_M1.jpg" xlink:type="simple" /> </jats:inline-formula>) IR- improved soft-wall AdS/QCD model at finite isospin chemical potential <jats:inline-formula> <jats:tex-math><?CDATA $\mu_I$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083106_M2.jpg" xlink:type="simple" /> </jats:inline-formula> and temperature <jats:italic>T</jats:italic>. By self-consistently solving the equations of motion, we obtain the phase diagram in the plane of <jats:inline-formula> <jats:tex-math><?CDATA $\mu_I$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083106_M3.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:italic>T</jats:italic>. The pion condensation appears together with a massless Nambu-Goldstone boson <jats:inline-formula> <jats:tex-math><?CDATA $m_{\pi_1}(T_c, \mu_I^c)=0$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083106_M4.jpg" xlink:type="simple" /> </jats:inline-formula>, which is very likely to be a second-order phase transition with mean-field critical exponents in the small <jats:inline-formula> <jats:tex-math><?CDATA $\mu_I$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083106_M5.jpg" xlink:type="simple" /> </jats:inline-formula> region. When <jats:inline-formula> <jats:tex-math><?CDATA $T=0$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083106_M6.jpg" xlink:type="simple" /> </jats:inline-formula>, the critical isospin chemical potential approximates to vacuum pion mass <jats:inline-formula> <jats:tex-math><?CDATA $\mu_I^c \approx m_0$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083106_M7.jpg" xlink:type="simple" /> </jats:inline-formula>. The pion condensed phase exists in an arched area, and the boundary of the chiral crossover intersects the pion condensed phase at a tri-critical point. Qualitatively, the results are in good agreement with previous studies on lattice simulations and model calculations. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the rare decays <jats:inline-formula> <jats:tex-math><?CDATA $\Lambda_b \rightarrow \Lambda l^+ l^-~(l=e,\mu, \tau)$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083107_M2.jpg" xlink:type="simple" /> </jats:inline-formula> in the Bethe-Salpeter equation approach. We find that the branching ratio is <jats:inline-formula> <jats:tex-math><?CDATA ${\rm Br}(\Lambda_b \rightarrow \Lambda \mu^+ \mu^-)\times 10^{6} = 1.051 \sim 1.098$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083107_M3.jpg" xlink:type="simple" /> </jats:inline-formula> in our model. This result agrees with the experimental data well. In the same parametric region, we find that the branching ratio is <jats:inline-formula> <jats:tex-math><?CDATA ${\rm Br}(\Lambda_b \rightarrow \Lambda e^+ e^-(\tau^+ \tau^-) )\times 10^{6} = 0.252 \sim $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083107_M4.jpg" xlink:type="simple" /> </jats:inline-formula> <jats:inline-formula> <jats:tex-math><?CDATA $ 0.392 ~(0.286 \sim 0.489)$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083107_M4-1.jpg" xlink:type="simple" /> </jats:inline-formula>. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>This exploratory study computes two-photon decay widths of pseudo-scalar ( <jats:inline-formula> <jats:tex-math><?CDATA $ \eta_c $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083108_M1.jpg" xlink:type="simple" /> </jats:inline-formula>) and scalar ( <jats:inline-formula> <jats:tex-math><?CDATA $ \chi_{c0} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083108_M2.jpg" xlink:type="simple" /> </jats:inline-formula>) charmonium using two ensembles of <jats:inline-formula> <jats:tex-math><?CDATA $ N_f = 2 $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083108_M3.jpg" xlink:type="simple" /> </jats:inline-formula> twisted mass lattice QCD gauge configurations. The simulation is performed using two lattice ensembles with lattice spacings <jats:inline-formula> <jats:tex-math><?CDATA $ a = 0.067 $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083108_M4.jpg" xlink:type="simple" /> </jats:inline-formula> fm with size <jats:inline-formula> <jats:tex-math><?CDATA $ 32^3\times{64} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083108_M5.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ a = 0.085 $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083108_M6.jpg" xlink:type="simple" /> </jats:inline-formula> fm with size <jats:inline-formula> <jats:tex-math><?CDATA $ 24^3\times{48} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083108_M7.jpg" xlink:type="simple" /> </jats:inline-formula>. The decay widths for the two charmonia are obtained within the expected ballpark, but are however smaller than the experimental ones. Possible reasons for these discrepancies are discussed. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>A Dvali–Gabadadze–Porrati (DGP) brane-world model with perfect fluid brane matter including a Brans-Dicke (BD) scalar field on brane was utilized to investigate the problem of the quark-hadron phase (QHP) transition in early evolution of the Universe. The presence of the BD scalar field arises with several modified terms in the Friedmann equation. Because the behavior of the phase transition strongly depends on the basic evolution equations, even a small change in these relations might lead to interesting results about the time of transition. The phase transition is investigated in two scenarios, namely the first-order phase transition and smooth crossover phase transition. For the first-order scenario, which is used for the intermediate temperature regime, the evolution of the physical quantities, such as temperature and scale factor, are investigated before, during, and after the phase transition. The results show that the transition occurs in about a micro-second. In the following part, the phenomenon is studied by assuming a smooth crossover transition, where the lattice QCD data is utilized to obtain a realistic equation for the state of the matter. The investigation for this part is performed in the high and low-temperature regimes. Using the trace anomaly in the high-temperature regime specifies a simple equation of state, which states that the quark-gluon behaves like radiation. However, in the low-temperature regime, the trace anomaly is affected by discretization effects, and the hadron resonance gas model is utilized instead. Using this model, a more realistic equation of state is found in the low-temperature regime. The crossover phase transition in both regimes is considered. The results determine that the transition lasts around a few micro-seconds. Further, the transition in the low-temperature regime occurs after the transition in the high-temperature regime.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We demonstrate that a scotogenic dark symmetry can be obtained as a residual subgroup of the global <jats:inline-formula> <jats:tex-math><?CDATA $U(1)_{B-L}$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083110_M1.jpg" xlink:type="simple" /> </jats:inline-formula> symmetry already present in the Standard Model. In addition, we propose a general framework in which the <jats:inline-formula> <jats:tex-math><?CDATA $U(1)_{B-L}$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083110_M2.jpg" xlink:type="simple" /> </jats:inline-formula> symmetry is spontaneously broken into an even <jats:inline-formula> <jats:tex-math><?CDATA ${\cal{Z}}_{2n}$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083110_M3.jpg" xlink:type="simple" /> </jats:inline-formula> subgroup, setting the general conditions for neutrinos to be Majorana and for dark matter stability to exist in terms of the residual <jats:inline-formula> <jats:tex-math><?CDATA ${\cal{Z}}_{2n}$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083110_M4.jpg" xlink:type="simple" /> </jats:inline-formula>. As an example, under this general framework, we build a class of simple models where, in a scotogenic manner, the dark matter candidate is the lightest particle running inside the mass loop of a neutrino. The global <jats:inline-formula> <jats:tex-math><?CDATA $U(1)_{B-L}$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_083110_M5.jpg" xlink:type="simple" /> </jats:inline-formula> symmetry in our framework, being anomaly free, can also be gauged in a straightforward manner leading to a richer phenomenology. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study heavy flavor properties at finite temperature in the framework of a relativistic potential model. Using an improved method to solve the three-body Dirac equation, we determine a universal set of model parameters for both mesons and baryons by fitting heavy flavor masses in vacuum. Taking heavy quark potential from lattice QCD simulations in hot medium, we systematically calculate heavy flavor binding energies and averaged sizes as functions of the temperature. The meson and baryons are separately sequentially dissociated in the quark-gluon plasma, and the mesons can survive at higher temperatures owing to the stronger potential between quark-antiquark pairs than that between quark-quark pairs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, we analyze the electroproduction of the LHCb pentaquark states with the assumption that they are resonant states. Our main concern is to investigate the final state distribution in the phase space to extract a feeble pentaquark signal from a large non-resonant background. The results indicate that the signal to background ratio will increase significantly with a proper kinematic cut, which will be beneficial for future experimental analysis.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, two novel improvements for the theoretical calculation of neutron distributions are presented. First, the available experimental proton distributions are used as a constraint rather than inferred from the calculation. Second, the recently proposed distribution formula, d3pF, is used for the neutron density, which is more detailed than the usual shapes, for the first time in a nuclear structure calculation. A semi-microscopic approach for binding energy calculation is considered in this study. However, the proposed improvements can be introduced to any other approach. The ground state binding energy and neutron density distribution of <jats:sup>208</jats:sup>Pb nucleus are calculated by optimizing the binding energy considering three different distribution formulae. The implementation of the proposed improvements leads to qualitative and quantitative improvements in the calculation of the binding energy and neutron density distribution. The calculated binding energy agrees with the experimental value, and the calculated neutron density exhibits fluctuations within the nuclear interior, which corresponds with the predictions of self-consistent approaches. </jats:p>