Charm mesons in magnetized nuclear matter -- effects of (inverse) magnetic catalysis

We investigate the in-medium masses of the pseudoscalar $(D,{\bar D},D_s^{\pm})$, and vector $(D^*,\bar{D}^*, D_s^{*\pm})$, open charm mesons in isospin asymmetric magnetized nuclear matter, accounting for the effects of Dirac sea. The masses are used to study the in-medium partial decay widths of $D^* \rightarrow D \pi$ ($\bar{D}^*\rightarrow \bar{D}\pi$) and $\Psi(3770) \rightarrow D \bar{D}$, using the $^3P_0$ model. The in-medium masses of the open charm mesons are calculated from their interactions with the nucleons and scalar mesons within the generalized chiral effective model, in terms of the scalar and number densities of nucleons and the scalar fields fluctuations. The effects of Landau energy levels of protons and AMMs of the nucleons are also considered in the magnetized nuclear matter. The light quark condensates are modified considerably with magnetic field, leading to (inverse) magnetic catalysis due to the magnetized Dirac sea effects. The magnetic field causes modifications to occur due to the mixing of the pseudoscalar and longitudinal component of the vector mesons, along with the lowest Landau level contribution to the ground state energy of the charged mesons as point particle correction. For the charmonium state $\Psi(3770)$, the effects of the magnetized Dirac sea are incorporated to the mass modifications through the medium modified scalar dilaton field $\chi$ within the chiral model. The in-medium masses and decay widths of the open charm and charmonium mesons thus obtained should have important observable consequences in the production of the open charm mesons and charmonia in peripheral ultra-relativistic heavy ion collision experiments, where huge magnetic fields are expected to be created.Comment: 40 pages, 15 figures, version published in Phys. Rev. C 104,065204 (2023

Open bottom mesons in magnetized matter -- effects of (inverse) magnetic catalysis

In-medium masses of the pseudoscalar and vector open bottom mesons ($B$, $\bar{B}$ and $B^*$ and $\bar{B}^*$) 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 of the medium, calculated in terms of the scalar and number densities of the nucleons and the scalar fields' fluctuations, within the chiral model. The effects of magnetized Dirac sea lead to considerable changes in the scalar fields with increasing magnetic field, which are related to the chiral condensates. There is observed to be an enhancement (reduction) in the light quark condensates condensates with rising magnetic field, a phenomenon called (inverse) magnetic catalysis. The contribution of the magnetic field on the Fermi sea of nucleons are also taken into account through protons Landau energy levels and nucleons anomalous magnetic moments (AMMs). The additional contribution of the lowest Landau level for the charged mesons are taken into account. In presence of an external magnetic field, the PV mixing effects between the longitudinal component of the vector mesons and the pseudoscalar mesons ($B-B^{*||}$ and $\bar{B}-\bar{B}^{*||}$) are studied, which lead to a level repulsion between their masses, increasing with magnetic field. The magnetic fields are observed to have significant contributions on the in-medium masses of the open bottom mesons through the contribution of the Dirac sea (DS), in particular, when the anomalous magnetic moments (AMMs) are taken into consideration.Comment: 25 pages, 10 figures. arXiv admin note: text overlap with arXiv:2208.0585

QCD sum rule analysis of Heavy Quarkonium states in magnetized matter -- effects of (inverse) magnetic catalysis

The masses of the $1S$ and $1P$ states of heavy quarkonia are investigated in the magnetized, asymmetric nuclear medium, accounting for the Dirac sea effects, using a combined approach of chiral effective model and QCD sum rule method. These are calculated from the in-medium scalar and twist-2 gluon condensates, calculated within the chiral model. The gluon condensate is simulated through the scalar dilaton field, $\chi$ introduced in the model through a scale-invariance breaking logarithmic potential. Considering the scalar fields to be classical, the dilaton field, $\chi$, the non-strange isoscalar, $\sigma (\sim (\langle \bar u u\rangle +\langle \bar d d\rangle ))$, strange isoscalar, $\zeta (\sim \langle \bar s s\rangle)$ and non-strange isovector, $\delta (\sim (\langle\bar u u\rangle-\langle\bar d d\rangle)$) fields, are obtained by solving their coupled equations of motion, as derived from the chiral model Lagrangian. The effects of magnetic field due to the Dirac sea as well as the Landau energy levels of protons, and the non-zero anomalous magnetic moments of the nucleons are considered in the present study. In presence of an external magnetic field, there is also mixing between the longitudinal component of the vector meson and pseudoscalar meson (PV mixing) in both quarkonia sectors, leading to a rise (drop) of the masses of $J/\psi^{||}\ (\eta_c$) and $\Upsilon^{||}(1S)\ (\eta_b$) states. These might show in the experimental observables, e.g., the dilepton spectra in the non-central, ultra-relativistic heavy ion collision experiments at RHIC and LHC, where the produced magnetic field is huge.Comment: 35 pages, 20 figures. arXiv admin note: text overlap with arXiv:2104.0547

Thermal dependency of RAG1 self-association properties

<p>Abstract</p> <p>Background</p> <p>Functional immunoglobulin and T cell receptor genes are produced in developing lymphocytes by V(D)J recombination. The initial site-specific DNA cleavage steps in this process are catalyzed by the V(D)J recombinase, consisting of RAG1 and RAG2, which is directed to appropriate DNA cleavage sites by recognition of the conserved recombination signal sequence (RSS). RAG1 contains both the active site and the RSS binding domains, although RAG2 is also required for DNA cleavage activity. An understanding of the physicochemical properties of the RAG proteins, their association, and their interaction with the RSS is not yet well developed.</p> <p>Results</p> <p>Here, we further our investigations into the self-association properties of RAG1 by demonstrating that despite the presence of multiple RAG1 oligomers, only the dimeric form maintains the ability to interact with RAG2 and the RSS. However, facile aggregation of the dimeric form at physiological temperature may render this protein inactive in the absence of RAG2. Upon addition of RAG2 at 37°C, the preferentially stabilized V(D)J recombinase:RSS complex contains a single dimer of RAG1.</p> <p>Conclusion</p> <p>Together these results confirm that the functional form of RAG1 in V(D)J recombination is in the dimeric state, and that its stability under physiological conditions likely requires complex formation with RAG2. Additionally, in future structural and functional studies of RAG1, it will be important to take into account the temperature-dependent self-association properties of RAG1 described in this study.</p

Measurement of the top quark forward-backward production asymmetry and the anomalous chromoelectric and chromomagnetic moments in pp collisions at √s = 13 TeV

Abstract The parton-level top quark (t) forward-backward asymmetry and the anomalous chromoelectric (d̂ t) and chromomagnetic (μ̂ t) moments have been measured using LHC pp collisions at a center-of-mass energy of 13 TeV, collected in the CMS detector in a data sample corresponding to an integrated luminosity of 35.9 fb−1. The linearized variable AFB(1) is used to approximate the asymmetry. Candidate t t ¯ events decaying to a muon or electron and jets in final states with low and high Lorentz boosts are selected and reconstructed using a fit of the kinematic distributions of the decay products to those expected for t t ¯ final states. The values found for the parameters are AFB(1)=0.048−0.087+0.095(stat)−0.029+0.020(syst),μ̂t=−0.024−0.009+0.013(stat)−0.011+0.016(syst), and a limit is placed on the magnitude of | d̂ t| &lt; 0.03 at 95% confidence level. [Figure not available: see fulltext.

Electroweak production of two jets in association with a Z boson in proton-proton collisions root s =13 TeV

A measurement of the electroweak (EW) production of two jets in association with a Z boson in proton-proton collisions at root s = 13 TeV is presented, based on data recorded in 2016 by the CMS experiment at the LHC corresponding to an integrated luminosity of 35.9 fb(-1). The measurement is performed in the lljj final state with l including electrons and muons, and the jets j corresponding to the quarks produced in the hard interaction. The measured cross section in a kinematic region defined by invariant masses m(ll) > 50 GeV, m(jj) > 120 GeV, and transverse momenta P-Tj > 25 GeV is sigma(EW) (lljj) = 534 +/- 20 (stat) fb (syst) fb, in agreement with leading-order standard model predictions. The final state is also used to perform a search for anomalous trilinear gauge couplings. No evidence is found and limits on anomalous trilinear gauge couplings associated with dimension-six operators are given in the framework of an effective field theory. The corresponding 95% confidence level intervals are -2.6 <cwww/Lambda(2) <2.6 TeV-2 and -8.4 <cw/Lambda(2) <10.1 TeV-2. The additional jet activity of events in a signal-enriched region is also studied, and the measurements are in agreement with predictions.Peer reviewe

Measurement of the Splitting Function in &ITpp &ITand Pb-Pb Collisions at root&ITsNN&IT=5.02 TeV

Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions, but it is not known where in the shower evolution the modifications occur. The momentum ratio of the two leading partons, resolved as subjets, provides information about the parton shower evolution. This substructure observable, known as the splitting function, reflects the process of a parton splitting into two other partons and has been measured for jets with transverse momentum between 140 and 500 GeV, in pp and PbPb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair. In central PbPb collisions, the splitting function indicates a more unbalanced momentum ratio, compared to peripheral PbPb and pp collisions.. The measurements are compared to various predictions from event generators and analytical calculations.Peer reviewe

An embedding technique to determine ττ backgrounds in proton-proton collision data

An embedding technique is presented to estimate standard model tau tau backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed mu mu events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS. Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at root s = 13 TeV corresponding to an integrated luminosity of 41.5 fb(-1).Peer reviewe

Measurement of nuclear modification factors of gamma(1S)), gamma(2S), and gamma(3S) mesons in PbPb collisions at root s(NN)=5.02 TeV

The cross sections for ϒ(1S), ϒ(2S), and ϒ(3S) production in lead-lead (PbPb) and proton-proton (pp) collisions at √sNN = 5.02 TeV have been measured using the CMS detector at the LHC. The nuclear modification factors, RAA, derived from the PbPb-to-pp ratio of yields for each state, are studied as functions of meson rapidity and transverse momentum, as well as PbPb collision centrality. The yields of all three states are found to be significantly suppressed, and compatible with a sequential ordering of the suppression, RAA(ϒ(1S)) > RAA(ϒ(2S)) > RAA(ϒ(3S)). The suppression of ϒ(1S) is larger than that seen at √sNN = 2.76 TeV, although the two are compatible within uncertainties. The upper limit on the RAA of ϒ(3S) integrated over pT, rapidity and centrality is 0.096 at 95% confidence level, which is the strongest suppression observed for a quarkonium state in heavy ion collisions to date. © 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.Peer reviewe