Search

A number of absolute moment-based upper bounds for Gini's mean difference are extended to general L-moments. Improvement of some bounds by alternative choice of centre for the absolute moments is explored. Different bounds are compared numerically. The distribution for which upper bounds for Gini's mean difference are attained is given. Extension is made to trimmed L-moments and hence to probability weighted moments. [ABSTRACT FROM AUTHOR]

Scientists have successfully accelerated a beam of muons, which are heavy relatives of electrons, in a development that could lead to new particle physics experiments. By cooling down and reaccelerating muons in a specific direction, researchers at the Japan Proton Accelerator Research Complex created muonium, a combination of muons and electrons. The muons were then accelerated to a speed of approximately 12,000 kilometers per second, offering potential for future particle colliders to uncover physics secrets. This advancement opens up possibilities for further exploration in the field of particle physics. [Extracted from the article]

There is increasing interest in deep exclusive meson production (DEMP) reactions, as they provide access to Generalized Parton Distributions over a broad kinematic range, and are the only means of measuring pion and kaon charged electric form factors at high Q 2. Such investigations are a particularly useful tool in the study of hadronic structure in QCD's transition regime from long-distance interactions described in terms of meson-nucleon degrees of freedom, to short-distance interactions governed by hard quark-gluon degrees of freedom. To assist the planning of future experimental investigations of DEMP reactions in this transition regime, such as at Jefferson Lab and the Electron-Ion Collider (EIC), we have written a special purpose event generator, DEMPgen. Currently, DEMPgen can generate the following reactions: t -channel p (e , e ′ π +) n , p (e , e ′ K +) Λ [ Σ 0 ] , and n → (e , e ′ π −) p from a polarized 3He target. DEMPgen is modular in form, so that additional reactions can be added over time. The generator produces kinematically-complete reaction events which are absolutely-normalized, so that projected event rates can be predicted, and detector resolution requirements studied. The event normalization is based on parameterizations of theoretical models, appropriate to the kinematic regime under study. Both fixed target modes and collider beam modes are supported. This paper presents the structure of the generator, the model parameterizations used for absolute event weighting, the kinematic distributions of the generated particles, some initial results using the generator, and instructions for its use. PROGRAM SUMMARY Program title: DEMPgen CPC Library link to program files: https://doi.org/10.17632/3nxcm5fsdz.1 Developer's repository link: https://github.com/JeffersonLab/DEMPgen/releases Licensing provisions: GNU General Public License 3 Programming language: C++ External package: ROOT Nature of problem: Despite the increasing interest in deep exclusive meson production (DEMP) reactions, no physics event generator currently exists for these types of reactions. Such a generator is needed for the planning of future experimental investigations at Jefferson Lab and the Electron-Ion Collider (EIC), so we have undertaken to write a special purpose event generator, DEMPgen. Solution method: DEMPgen produces kinematically-complete reaction events which are absolutely-normalized, so that projected event rates can be predicted, and detector resolution requirements studied. The event normalization is based on parameterizations of theoretical models, appropriate to the kinematic regime under study. The following reactions can be generated: t -channel p (e , e ′ π +) n , p (e , e ′ K +) Λ [ Σ 0 ] , and n → (e , e ′ π −) p from a polarized 3He target. These reactions have been parameterized for kinematic regimes relevant to experiments at SoLID and the EIC (as described in Secs. 3.1, 3.2). DEMPgen is modular in form, so that additional reactions can be added over time. Both fixed target modes and collider beam modes are supported. Additional comments including restrictions and unusual features: DEMPgen events have variable weights, which must be included to yield realistic distributions and rate projections, see Secs. 3.1.2, 3.3.6 for more details. DEMPgen does not yet include the radiative tail contributions for exclusive lepton-hadron reactions. This is a planned future upgrade, along with other upgrades described in Sec. 5. Developer's repository maintained by Department of Physics, University of Regina. [ABSTRACT FROM AUTHOR]

In this article, the author discusses the anomalies in physics. Topics discussed include model of particle physics with the quantum-theory-based melange, imbalance in decays of particles known as mesons and anomalies in the cosmic microwave with the equations of the general relativity. It mentions that neutrinos are the particles that interact only via the weak nuclear force that governs radioactive decay.

A recent study conducted by researchers at the University of Nevada focused on the potential health risks posed by galactic cosmic rays (GCR) during a human mission to Mars. GCR consists of high energy protons and heavier ions that can penetrate spacecraft and reach human organs. The study specifically examined the tissue-specific dose equivalents and effective dose of secondary mesons and leptons, which are generated when GCR interacts with shielding materials and human tissues. The results showed that secondary mesons and leptons contribute to a small percentage of the total effective dose, providing valuable insights into the health risks associated with space exploration missions. [Extracted from the article]

This article reports that for 30 years, researchers have been battling to make sense of the strong force, the glue that sticks protons and neutrons together in nuclei. Yet their best mathematical theory has been so complex that no one could turn the dense equations into useful predictions. Now all that is changing, thanks to the supercomputer's calculations. By assembling a working virtual replica of protons and other subatomic particles such as D-mesons, the work opens up a completely new way of finding physics beyond the standard model, physicists' best theory about the particles and forces in nature. This promising approach is based on a theory called quantum chromodynamics (QCD) and it goes by the name of lattice QCD. It has enjoyed a reversal of fortune in the past few months after many years when it was considered a poor relation of particle physics. While experiments churned out particles whose behaviour shed light on the internal workings of the strong force, lattice QCD theorists were left playing catch-up.

Discusses the strengths and weaknesses of the Standard Model of particle physics. Explaining the excess of matter in the universe; Disparities in the behavior of matter and antimatter; Symmetry called charge-parity reversal (CP); Particle interactions according to the Standard Model; Role of mesons; Symmetry and charge conjugation; Movement of a particle and its antiparticle; Supporting research for CP; Birth of a skewed universe; More. INSET: Reversal of charge and parity.

The article recounts the events surrounding the discovery and production of the omega-minus particle, which may support the organization of particles inside the atomic nucleus as proposed by Murray Gell-Man of the California Institute of Technology and independently by Yuval Ne'eman of Tel Aviv University in Israel. Omega-minus particle would be produced from K-minus mesons shot in the bubble chamber to interact with a proton in the liquid hydrogen.

The article presents a study about artificial atom in which an electron is replaced with a meson. Mesons are middleweight particles which are about the weight between an electron and proton, and are be connected with the forces inside the atomic nucleus. Scientist Niels Bohr points out that if energy is supplied to the atom, the electron may leave its orbit and jump momentarily to an orbit farther from the nucleus.

Focuses on a study of how the study of one subject can lead to another subject of exotic atoms that involves both high-energy physics and nuclear physics. Characteristics of exotic atoms; Steps in making exotic atoms with negative mesons; Kinds of exotic atoms and their behavior; Significant aspect of kaonic reaction.

Provides information on the high-energy scattering of the fundamental particles of matter. Overview of high-energy collision between a fast-moving negative pion, or pi meson, and a stationary proton; Evolution of the creation and study of the subnuclear constituents of matter; Discussion on the assumption that energy momentum and electric charge are conserve in scattering events; Discussion on the interactions of fundamental particle.

We discuss and compare the efficiency of various methods, combinations of point-to-all propagators, stochastic timeslice-to-all propagators, the one-end trick and sequential propagators, to compute two-point correlation functions of two-quark and four-quark interpolating operators of different structure including quark–antiquark type, mesonic molecule type, diquark–antidiquark type and two-meson type. Although we illustrate our methods in the context of the a 0 ( 980 ) , they can be applied for other multi-quark systems, where similar diagrams appear. Thus our results could provide helpful guidelines on the choice of methods for correlation function computation for future lattice QCD studies of meson–meson scattering and possibly existing tetraquark states. [ABSTRACT FROM AUTHOR]

Ultra-peripheral collisions (UPCs) have been a significant source of study at RHIC and the LHC. In these collisions, the two colliding nuclei interact electromagnetically, via two-photon or photonuclear interactions, but not hadronically; they effectively miss each other. Photonuclear interactions produce vector meson states or more general photonuclear final states, while two-photon interactions can produce lepton or meson pairs, or single mesons. In these interactions, the collision geometry plays a major role. We present a program, STARlight, that calculates the cross-sections for a variety of UPC final states and also creates, via Monte Carlo simulation, events for use in determining detector efficiency. Program summary Program Title : STARlight (v2.2) Program Files doi : http://dx.doi.org/10.17632/xjpf4rxtbj.1 Licensing provisions : GNU GPLv3 Programming Language : C++ External Routines : PYTHIA 8.2 and DPMJET 3.0 are needed for some final states. Nature of problem : The cross-section for ultra-peripheral collisions is obtained by integrating the photon fluxes in transverse impact parameter space, subject to the requirement (which is also impact parameter dependent) that the colliding nuclei do not interact hadronically. The program is a two step process. First, it calculates the cross-sections for the reaction of interest, as a function of W (photon–Pomeron or two-photon center of mass energy), Y (final state rapidity) and p T (final state transverse momentum). Second, STARlight generates Monte Carlo events which can be used to determine cross-sections within specific kinematic constraints or for studies of detector efficiencies. The second step includes the decay of any unstable particles produced in the reaction, with appropriate consideration of particle spins and parity. It outputs these events in ASCII format. Solution method : The program generates a two dimensional look-up table of the production cross-section as a function of final state rapidity and mass. The dimensions of the table are selectable, allowing the user to choose the desired accuracy. For certain final states, a second two-dimensional look-up table, giving the transverse momentum distribution, as a function of rapidity, is also used. With these look-up tables, the program generates final states. Particle decays and the final angular distributions are calculated for each event. Restrictions : The program is focused on ultra-relativistic collisions at Brookhaven’s RHIC (Relativistic Heavy Ion Collider) and CERN’s LHC (Large Hadron Collider), with final states that are visible in a central detector. At lower energies (i.e., at the CERN SPS), caution should be exercised because STARlight does not account for the longitudinal momentum transfer to the nucleus; this is larger at low beam energies. References: http://starlight.hepforge.org and references in this article. [ABSTRACT FROM AUTHOR]

The article focuses on the discovery of charm as a property of matter. The particle psi serves as the first evidence on the existence of charm. This particle is an hadron which is made up of the more fundamental entities called quarks. The psi is also known to be a meson which is made up of charm quark and charm antiquark. It was found that this particle and the electron-positron atom are analogous in some way.

The article describes an experiment carried out at the Brookhaven National Laboratory by Val L. Fitch, James H. Christenson, James W. Cronin and Rene Turlay of Princeton University regarding the so-called fifth force in nature. They found that two times out of 1,000 the K-two-zero meson decays into two pi mesons instead of three pi mesons.

Since the end of the war the focus of interest in physical science has not been the atomic pile or the atom bomb but a family of unfamiliar sub-atomic particles known as mesotrons or mesons. Mesons are among the debris left when atoms in the earth's atmosphere are struck by cosmic rays, the mysterious super-powerful radiation that rains ceaselessly on the earth from outer space. The great interest in mesons arises from the fact that they are taking physicists into a new world. The release of atomic energy in the atomic pile and bomb conveys the impression that few secrets remain to the atom.

Reports on the identification of two new subatomic particles from several photographs of nuclear events at the Brookhaven National Laboratory in New York in 1969. Prediction on the existence of the particles by the SU(3) theory of elementary particles; Application of the theory on interacting particles baryons and mesons; Members of the xi class particles that were identified before the subatomic particles.

The article discusses the decay of unstable particle D0 mesons, consisting of charm quarks, compared with the decay of their antimatter counterparts, referencing research at the Large Hadron Collid­er Beauty (LHCb) in CERN Switzerland.

The article reports on research by Tomasz Skwarnicki at Syracuse University in New York on how a pentaquark forms from a baryon and a meson.

ASTRONOMERS HAVE TRACED dozens of neutrinos back to the nearby galaxy NGC 1068 (M77), only the second individual source known to produce copious amounts of the uncharged, almost massless particle. The high-energy neutrinos were likely a byproduct of particle collisions near the supermassive black hole that sits in the galaxy's core. Indeed, we need more than blazars to explain all the high-energy neutrinos IceCube detects, writes Kohta Murase (Penn State) in an accompanying commentary in Science. [Extracted from the article]

A newly upgraded version of the BCVEGPY, a generator for hadronic production of the meson B c and its excited states, is available. In comparison with the previous one (Chang et al., 2006), the new version is to apply an improved hit-and-miss technology to generating the un-weighted events much more efficiently under various simulation environments. The codes for production of 2 S -wave B c states are also given here. New version program summary Title of program : BCVEGPY2.2 Catalogue identifier : ADTJ_v2_3 Program obtained from : CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions : Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc. : 323731 No. of bytes in distributed program, including test data, etc. : 4498602 Distribution format : tar.gz Computer : Any LINUX based on PC with FORTRAN 77 or FORTRAN 90 and GNU C compiler as well Operating systems : LINUX Programming language used : FORTRAN 77/90 Memory required to execute with typical data : About 2.0 MB Classification : 11.2, 11.5 Catalogue identifier of previous version : ADTJ_v2_2 Journal reference of previous version : Comput. Phys. Commun. 183 (2012) 442 Does the new version supersede the old version? : Yes Nature of physical problem : Hadronic Production of B c meson and its excited states. Method of solution : To generate un-weighted events of B c meson and its excited states by using an improved hit-and-miss technology. Reasons for new version : Responding to the feedback from users, such as those from CMS and LHCb groups, we create a new hit-and-miss algorithm for generating the un-weighted events. Furthermore, the relevant codes for generating the 2 S -excited state of B c meson are added, because the excited state production may be sizable in the new LHC run. Typical running time : It depends on which option is chosen to match PYTHIA when generating the full events and also on which state of B c meson, either its ground state or its excited states, is to be generated. Typically on a 2.27GHz Intel Xeon E5520 processor machine, for producing the B c meson ground state: I) If setting [IDWTUP = 3 and unwght = .true.], it shall adopt the new hit-and-miss technology to generate the un-weighted events, and to generate 10 5 events takes 30 minutes; II) If setting [IDWTUP = 3 and unwght = .false.] or [IDWTUP = 1 and IGENERATE = 0 ], it shall generate the weighted events, and to generate 10 5 events takes 2 minutes only (the fastest way, for theoretical purpose only); III) As a comparison, if setting [IDWTUP = 1 and IGENERATE = 1 ], it shall, as the same as the previous version, adopt the PYTHIA inner hit-and-miss technology to generate the un-weighted events, and to generate 1000 events takes about 22 hours. Thus, the efficiency (and accuracy also) for generating the un-weighted events obviously is greatly increased. Keywords : Event generator; Hadronic production; B c meson; Un-weighted events Summary of revisions : 1). We improve the approach for generating un-weighted events. 2). Responding to the feedback from users, we adjust part of the codes to make it work more user-friendly. More specifically, we explain main changes in the following : • Event generation . If each simulated event comes with a weight, it will make the data analysis much more complicated. Thus the un-weighted events are usually adopted for Monte Carlo simulations. As an external process of PYTHIA, the generator BCVEGPY [1–4] shall call the PYTHIA inner hit-and-miss mechanism to generate the un-weighted events by setting IDWGTUP = 1 and IGENERATE = 1 [5] , i.e. the Von Neumann method is used for generating the un-weighted B c events. Every events bearing a weight ( xwgtup ) respectively, when inputting them to PYTHIA, they are suffered from being accepted or rejected, all the fully generated events at the output become to have a common weight. The Von Neumann method states that the event should be accepted by the PYTHIA subroutine PYEVNT with a probability R = xwgtup / xmaxup . This can be achieved by comparing R with a random number that is uniformly distributed within the region of [ 0 , 1 ] . Namely if R is bigger than such a random number then the event is accepted, otherwise it should be rejected. Here xmaxup stands for the maximum event weight. The von Neumann method works effectively for the cases when all the weights of input events are moderate in the whole phase-space. However if the input events’ weights vary greatly, such as varying logarithmically, then its efficiency shall be greatly depressed, since too much time shall be wasted for calculating xwgtup of the rejected events. Thus it is helpful to find a new method for generating un-weighted events. We will adopt the new hit-and-miss strategy suggested by Ref. [6] to do the B c meson un-weight simulation. Extra switches for calling this new technology are added to BCVEGPY, e.g. the new hit-and-miss technology shall be called by setting IDWTUP = 3 and unwght = .true.. Details for this new technology can be found in Ref. [6] . For self-consistency, we repeat its main idea here. To be different from previous versions, BCVEGPY2.2 uses the VEGAS [7] and the MINT [8] as a combined way to generate the un-weighted events. The whole phase space shall be separated to a multi-dimensional phase-space grid. The main purpose of VEGAS [7] is to perform the adaptive Monte Carlo multi-dimensional integration, which uses the importance-sampling method to improve the integration efficiency. Each event shall generally result in a different weight, recorded by xwgtup , and the maximum weight within each grid shall be simultaneously recorded into the importance-sampling grid file (with the suffix .grid). Then following the idea of MINT, the Von Neumann method is used in each phase-space grid. Within this small grid region, the von Neumann algorithm works effectively, thus the efficiency for generating un-weighted events are greatly increased. To implement the new hit-and-miss algorithm into BCVEGPY2.2, we change the original VEGAS subroutine as vegas(fxn,ndim,ncall,itmx,nprn,xint,xmax,imode) Three new variables xint , xmax and imode are added in the VEGAS subroutine. The xmax array is used to record the maximum weights in all cells and imode is a flag. xint stands for the output cross-section when setting imode=0 , which shall be used to initialize the xmax array when setting imode=1 . For convenience, the generated xmax array will be stored in the same grid file in which the importance sampling function is stored. In the initialization stage, the VEGAS subroutine shall be called by the subroutine evntinit twice by setting imode=0 and imode=1 respectively to generate both the upper bound grid xmax for all cells and the importance sampling function. A subroutine gen(fxn,ndim,xmax,jmode) is defined in the file vegas.F with the purpose to generate the un-weighted events. Three options for calling gen subroutine are defined: jmode=0 is to initializes the parameter; jmode=3 is to print the generation statistics; jmode=1 is the key option, which is to use the new hit-and-miss technology to generate the un-weighted events. More explicitly, by calling gen(fxn,ndim,xmax,jmode=1) , three steps shall be executed: 1. Call the phase_gen subroutine to generate a random phase-space point and to calculate its weight xwgtup . 2. Judge the point locates in which cell and read from the xmax array and get the upper bound value xmaxup for this particular cell. 3. Judge whether such point be kept or not by using the Von Neumann method with the help of the probability xwgtup / xmaxup . To be more flexible, we add one parameter igenmode for generating or using the existed .grid files. When setting igenmode=1 , the VEGAS subroutine shall be called to generate the .grid files. When setting igenmode=2 , the VEGAS subroutine shall be called to generate more accurate .grid files from the existed .grid files. When setting igenmode=3 , one can directly use the existed .grid files to generate events without running VEGAS. Importantly, before using the existed .grid files, one must ensure all the parameters be the same as the previous generation. • A script for setting the parameters and a cross-check of the un-weighted events. We put an additional file, bcvegpy_set_par.nam , in the new version for setting the parameters. This way the user does not need to compile the program again if only the parameter values are changed. Fig. 1 Comparison of the normalized B c transverse momentum ( P T ) and rapidity ( y ) distributions derived by setting unwght =.true. (events) and unwght =.false. (differential distributions), which are represented by solid and dotted lines, respectively. As a cross-check of the new technology, we compare the un-weighted B c event distributions derived by setting unwght =.true. with the weighted B c differential distributions derived by setting unwght =.false.. The results are shown in Fig. 1 . Those two distributions after proper normalization agree well with each other, that shows our present scheme for un-weighted events is correct. • Bc(2S) generation . In 2014 the ATLAS collaboration reported an observation about an excited state of B c meson, which most probably is B c ( 2 S ) state [9] . With more data being collected at LHC detectors, it is hopeful that more observations on the excited B c states will be issued. Therefore in addition to the production via color-singlet B c ( 1 S ) , B c ( 1 P ) and color-octet B c ( 1 S ) states, the B c ( 2 S ) production is involved in BCVEGPY2.2. It is achieved by replacing the 1 S -wave bound-state parameters pmb , pmc and fbc with those of the 2 S -wave one. Here pmb , pmc and fbc are for b -quark mass, c -quark mass and the radial wave function at the zero ( | R ( 0 ) | ), respectively. For the 2 S -wave case, their default values are set as pmb = 5.234 GeV , pmc = 1.633 GeV and fbc = 0.991 GeV 3 / 2 [10] if the mass of the 2 S -wave B c state is 6.867 GeV . More explicitly, two new values for ibcstate are added: ibcstate = 9 is to generate 2 1 S 0 state and ibcstate = 10 is to generate 2 3 S 1 state. Detailed technologies for deriving the production properties of all the mentioned ten B c meson states can be found in Refs. [11–13] . Furthermore, the values for mix_type are rearranged. mix_type=1 is to generate the mixing events for all mentioned states. mix_type=2 is to generate the mixing events for 1 1 S 0 and 1 3 S 1 states. mix_type=3 is to generate the mixing events for the four 1 P -wave states and the two color-octet 1 1 S 0 and 1 3 S 1 states. mix_type=4 is to generate the mixing events for 2 1 S 0 and 2 3 S 1 states. [ABSTRACT FROM AUTHOR]

We present spin-independent and spin-spin interquark potentials for the charmonium and charmed-strange mesons, which are calculated in 2+1 flavor lattice QCD simulations using the PACS-CS gauge configurations generated at the lightest pion mass (Mπ≈156(7) MeV) with a lattice cutoff of a-1≈2.2 GeV and a spatial volume of (3 fm)3. For the charm quark, we use a relativistic heavy quark (RHQ) action with fine tuned RHQ parameters, which closely reproduce both the experimental spin-averaged mass and hyper-fine splitting of the 1S charmonium. The interquark potential and the quark kinetic mass, both of which are key ingredients within the potential description of heavy-heavy and heavy-light mesons, are determined from the equal-time Bethe-Salpeter (BS) amplitude. The charmonium potentials are obtained from the BS wave function of 1S charmonia (ηc and J/ψ mesons), while the charmed-strange potential are calculated from the Ds and D*s heavy-light mesons. We then use resulting potentials and quark masses as purely theoretical inputs so as to solve the nonrelativistic Schrödinger equation for calculating accessible energy levels of charmonium and charmed-strange mesons without unknown parameters. The resultant spectra below the DD¯ and DK thresholds excellently agree with well-established experimental data. [ABSTRACT FROM AUTHOR]

Studies of D and B meson decays into hadrons have been used to test the standard model in the last 15 years. A heavy meson decay involves the combined effects of a primary weak vertex and subsequent hadronic final-state interactions, which determine the shapes of Dalitz plots. The fact that final products involve light mesons indicates that the QCD vacuum is an active part of the problem. This makes the description of these processes rather involved and, in spite of its importance, phenomenological analyses tend to rely on crude models. Our group produced, some time ago, a schematic calculation of the decay D+ → K- π+π+, which provided a reasonable description of data. Its main assumption was the dominance of the weak vector current, which yields a nonfactorizable interaction. Here we refine that calculation by including the correct momentum dependence of the weak vertex and extending the energy ranges of ππ and Kπ subamplitudes present into the problem. These new features make the present treatment more realistic and bring theory closer to data. [ABSTRACT FROM AUTHOR]

We present a study of the process e+e- π±(DD¯*)¥ using data samples of 1092 pb-1 at √s = 4.23 GeV and 826 pb-1 at √s = 4.26 GeV collected with the BESIII detector at the BEPCII storage ring. With full reconstruction of the D meson pair and the bachelor π± in the final state, we confirm the existence of the charged structure Zc(3885)¥ in the (DD¯*)¥ system in the two isospin processes e+e-→ π++D0D*- and e+e- → π+D-D*0. By performing a simultaneous fit, the statistical significance of Zc(3885)165; signal is determined to be greater than 10σ, and its pole mass and width are measured to be Mpole = (3881.7 ± 1.6(stat) ± 1.6(syst)) MeV/c2 and Γpole = (26.6 ± 2.0(stat) ±2.1(syst)) MeV, respectively. The Bom cross section times the (DD¯*)¥ branching fraction (σ(e+e- →π+ tt±Zc(3885)¥) × Br(Zc(3885)¥ → (DD¯*)¥)) is measured to be (141.6 ± 7.9(stat) ± 12.3(syst)) pb at y/s = 4.23 GeV and (108.4 ± 6.9(stat) ± 8.8(syst)) pb at √s = 4.26 GeV. The polar angular distribution of the π+- Zc(3885)¥ system is consistent with the expectation of a quantum number assignment of JP = 1+ for Zc(3885)165. [ABSTRACT FROM AUTHOR]

We analyze various aspects of pion and kaon condensation in the framework of chiral perturbation theory. Considering a system at vanishing temperature and varying the isospin chemical potential and the strange quark chemical potential we reproduce known results about the phase transition to the pion condensation phase and to the kaon condensation phase. However, we obtain mesonic mixings and masses in the condensed phases that are in disagreement with the results reported in previous works. Our findings are obtained both by a theory group analysis and by direct calculation by means of the same low-energy effective Lagrangian used in previous works. We also study the leptonic decay channels in the normal phase and in the pion condensed phase, finding that some of these channels have a peculiar nonmonotonic behavior as a function of the isospin chemical potential. Regarding the semileptonic decays, we find that they are feeding processes for the stable charged pion state. [ABSTRACT FROM AUTHOR]

Flavor-changing neutral scalar interactions are a standard feature of generic multi-Higgs models. These are constrained by mixing in the neutral meson systems. We consider situations where there are natural cancellations in such contributions. In particular, when the spin-0 particle has both scalar and pseudoscalar couplings, one may have a self-cancellation. We illustrate one such partial cancellation with Branco-Grimus-Lavoura models. We also inquire whether the flavor-changing quark interactions can lead to new production mechanisms for a neutral scalar at LHC. [ABSTRACT FROM AUTHOR]

The light pseudoscalar mesons play a twofold role: they may or have to be regarded both as low-lying bound states of the fundamental degrees of freedom of quantum chromodynamics and as the (pseudo) Goldstone bosons of the spontaneously broken chiral symmetries of quantum chromodynamics. We interrelate these aspects in a single quantum-field-theoretic approach relying on the Bethe-Salpeter formalism in instantaneous approximation by very simple means: the shape of the pseudoscalar-meson Bethe-Salpeter wave function dictated by chiral symmetry is used in Bethe-Salpeter equations for bound states of vanishing mass, in order to deduce analytically the interactions which govern the bound states under study. In this way, we obtain exact Bethe-Salpeter solutions for pseudoscalar mesons, in the sense of establishing the rigorous relationship between, on the one hand, the relevant interactions and, on the other hand, the Bethe-Salpeter amplitudes that characterize the bound states. [ABSTRACT FROM AUTHOR]

Within the framework of QCD sum rules, we use the least-squares fitting method to investigate the first radial excitations of the nucleon and light mesons such as ρ, K*, π, and φ. The extracted masses of these radial excitations are consistent with the experimental data. In particular, we find that the decay constant of π(1300), which is the first radial excitation of n, is tiny and is strongly suppressed as a consequence of chiral symmetry. [ABSTRACT FROM AUTHOR]

A dynamical coupled-channels (DCC) model for neutrino-nucleon reactions in the resonance region is developed. Starting from the DCC model that we have previously developed through an analysis of πN,γN→πN,ηN,KΛ,KΣ reaction data for W≤2.1 GeV, we extend the model of the vector current to Q2≤3.0 (GeV/c)2 by analyzing electron-induced reaction data for both proton and neutron targets. We derive axial-current matrix elements that are related to the πN interactions of the DCC model through the partially conserved axial current (PCAC) relation. Consequently, the interference pattern between resonant and nonresonant amplitudes is uniquely determined. We calculate cross sections for neutrino-induced meson productions, and compare them with available data. Our result for the single-pion production reasonably agrees with the data. We also make a comparison with the double-pion production data. Our model is the first DCC model that can give the double-pion production cross sections in the resonance region. We also make comparison of our result with other existing models to reveal an importance of testing the models in the light of PCAC and electron reaction data. The DCC model developed here will be a useful input for constructing a neutrino-nucleus reaction model and a neutrino event generator for analyses of neutrino experiments. [ABSTRACT FROM AUTHOR]

Using abundant experimental information about charmed mesons together with recent research, we systematically study higher radial and orbital excitations in the charmed meson family by analyzing the mass spectrum and by calculating their Okubo-Zweig-Iizuka-allowed two-body decay behaviors. This phenomenological analysis reveals underlying properties of the newly observed charmed states D(2550), D*(2600), D*(2760), D(2750), DJ(2580), D*J(2650), D*J(2760), DJ(2740), DJ(3000), and D*J(3000) to provide valuable information about the charmed mesons still missing in experiments. [ABSTRACT FROM AUTHOR]

Relativistic light-front bound-state equations for mesons and baryons can be constructed in the chiral limit from the supercharges of a superconformal algebra which connect baryon and meson spectra. Quark masses break the conformal invariance, but the basic underlying supersymmetric mechanism, which transforms meson and baryon wave functions into each other, still holds and gives remarkable connections across the entire spectrum of light and heavy-light hadrons. We also briefly examine the consequences of extending the supersymmetric relations to double-heavy mesons and baryons. [ABSTRACT FROM AUTHOR]

We discuss the two-photon coupling of the lightest scalar meson on the basis of an extension of XPT. Using low-energy data on the pion form factor and the γγ → π+π-(π0π0) cross sections as inputs, we find Γ(σ → γγ)0.126 ≃ keV. The smallness of the result and the relative weight between its components, Γγγ → S1/Γγγ → ππ → S1≤1, suggests that the scalar 0++ meson is mainly a Q2Q2 state. [ABSTRACT FROM AUTHOR]

The production of quark-antiquark pairs along a color flux tube precedes the fragmentation of the tube. Because of local conservation laws, the production of a q-q pair will lead to correlations of adjacently produced mesons (mostly pions). Adjacently produced mesons however can be signalled by their rapidity difference Δy falling within the window of ∣Δy∣≲1/(dN/dy), on account of the space-time-rapidity ordering of produced mesons in a flux-tube fragmentation. Therefore, the local conservation laws of momentum, charge, and flavor will lead to a suppression of the angular correlation function dN/(dΔϕdΔy) for two mesons with opposite charges or strangeness on the near side at (Δϕ,Δy)~0, but an enhanced correlation on the back-to-back, away side at Δϕ~π, within the window of ∣Δy∣≲1/(dN/dy). These properties can be used as signatures for the fragmentation of a color flux tube. The gross features of the signature of flux-tube fragmentation for two oppositely charged mesons are qualitatively consistent with the STAR and NA61/SHINE angular correlation data for two hadrons with opposite charges in the low-pT region in high-energy pp collisions. [ABSTRACT FROM AUTHOR]

In this paper, low-energy scattering of the (D*...*)± meson system is studied within Liischer's finite-size formalism using Nf = 2 twisted-mass gauge field configurations. With three different pion mass values, the 5-wave threshold scattering parameters--namely the scattering length a0 and the effective range r0--are extracted in the JPC = l+- channel. Our results indicate that, in this particular channel, the interaction between the two vector charmed mesons is weakly repulsive in nature and hence it does not support the possibility of a shallow bound state for the two mesons, at least for the pion mass values being studied. However, these results might suffer from undetermined systematic errors due to low-lying states ignored in this exploratory study. Still, it provides some useful information on the nature of the newly discovered resonance-like structure Zc(4025) observed in various experiments. [ABSTRACT FROM AUTHOR]

For the flavor-singlet heavy quark system of charmonia, we compute the masses of the ground state mesons in four different channels: pseudoscalar [ηc (1S)], vector [J/Ψ (1S)], scalar אc0 (1P)] and axial vector [אc1] (IP)], as well as the weak decay constants of the ηc (1S) and J/Ψ (1S) and the charge radius of ηc (1S). The framework for this analysis is provided by a symmetry-preserving Schwinger-Dyson equation (SDE) treatment of a vector x vector contact interaction. The results found for the meson masses and the weak decay constants, for the spin-spin combinations studied, are in fairly good agreement with experimental data and earlier model calculations based upon Schwinger-Dyson and Bethe-Salpeter equations involving sophisticated interaction kernels. The charge radius of ηc (1S) is consistent with the results from refined SDE studies and lattice quantum chromodynamics. [ABSTRACT FROM AUTHOR]

Using a simple model in the context of the Dyson-Schwinger-Bethe-Salpeter approach, we investigate the effects of a dressed-quark-gluon vertex on pseudoscalar meson masses. In particular, we focus on the unequal-mass case and investigate heavy-light meson masses; in addition, we study the premise of the effective treatment of heavy quarks in our approach. [ABSTRACT FROM AUTHOR]

The η-η' mixing mass term due to the derivative coupling SU(3)xSU(3) symmetry breaking term, produces an additional momentum-dependent pole term for processes with η' but is suppressed in the η amplitude by a factor mη²/mη'². This seems to be the origin of the two-angle description of the pseudoscalar decay constants used in the literature. In this paper, by diagonalizing both the mixing mass term and the momentum-dependent mixing term, we show that the η-η' system can be described by a meson field renormalization and a new mixing angle θ which differs from the usual mixing angle θP by a small momentum-dependent mixing d term. This new mixing scheme with exact treatment of the momentum-dependent mixing term is actually simpler than the perturbation treatment and should be used in any determination of the η-η' mixing angle and the momentum-dependent mixing term. Assuming nonet symmetry for the η0 singlet amplitude, from the sum rules relating θ and d to the measured vector meson radiative decay amplitudes, we obtain consistent solutions: θ=-(13.99±3.1)°, d=0.12±0.03 from ρ→ηγ and η'→ργ decays, for ω, θ=-(15.47±3.1)°, d=0.11±0.03, and for Φ, θ=-(12.66±2.1)°, d=0.10±0.03. It seems that vector meson radiative decays would favor a small η-η' mixing angle and a small momentum-dependent mixing term. [ABSTRACT FROM AUTHOR]

Based on a sample of η' mesons produced in the radiative decay J/ ω → γη' in 1.31 x 109 J/ ω events collected with the BESIII detector, the decay η' → ωe+e- is observed for the first time, with a statistical significance of 8σ. The branching fraction is measured to be B(η' → ωe+e-) = (1.97 ± 0.34(stat) ±0.17(syst)) x 10-4, which is in agreement with theoretical predictions. The branching fraction of η' → ω γ is also measured to be (2.55 ± 0.03(stat) ± 0.16(syst)) x 10-2, which is the most precise measurement to date, and the relative branching fraction B(η' → ωe+e-)/Bη' → ω γ is determined to be (7.71 ± 1.34(stat) ±0.54(syst)) x 10-3. [ABSTRACT FROM AUTHOR]

The article focuses on the study which examines the low-energy scattering of the meson system within the Lüscher's finite-size formalism and the discovery of the resonance-like structure Zc(4025).

The article discusses the calculation of the open charm meson production of in the proton-proton scattering through kt-factorization approach and the revision of its semileptonic decays.

The article presents a study regarding the strategies to observe and measure the properties of bottomonium mesons.

The article presents a study that investigates the effects of a dressed-quark-gluon vertex on pseudoscalar heavy-light meson masses.

The article discusses a study which describes the mixing of ŋ-ŋ' system with a meson field renormalization.

The article discusses the study regarding the K-multi-ρ interactions which contains K-mesons through the ude of three-body interactions formalism with Faddeev equations' fixed-center approximation.

We discuss inclusive production of open charm mesons in proton-proton scattering at the BNL RHIC. The calculation is performed in the framework of kt-factorization approach which effectively includes higher-order pQCD corrections. Different models of unintegrated gluon distributions (UGDF) from the literature are used. We focus on UGDF models favored by the LHC data and on a new up-to-date parametrizations based on the HERA collider deep-inelastic scattering high-precision data. Results of the kt-factorization approach are compared to next-to-leading order collinear predictions. The hadronization of heavy quarks is done by means of fragmentation function technique. The theoretical transverse momentum distributions of charmed mesons are compared with recent experimental data of the STAR collaboration at √s=200 and 500 GeV. Theoretical uncertainties related to the choice of renormalization and factorization scales as well as due to the quark mass are discussed. A very good description of the measured integrated cross sections and differential distributions is obtained for the Jung setB0 CCFM UGDF. Revised charm and bottom theoretical cross sections corresponding to those measured recently by the STAR and PHENIX collaborations for semileptonic decays of D and B mesons are presented. Significant improvement in theoretical description of the nonphotonic electrons measurements is clearly obtained with respect to the previous studies within the kt-factorization. [ABSTRACT FROM AUTHOR]

It is well established that the forces between nucleons are transmitted by mesons. According to the meson theory, the quantitative explanation of the nuclear forces was extremely tentative and incomplete. But this theory presents a valuable point of view. It is fairly certain now that the nucleons within nuclear matter are in a state made rather different from their free condition by the proximity of other nucleons .Charge independence of nuclear forces demand the existence of neutral meson as amongst the same type of nucleons (P-P) or (N-N). This force demands the same spin and the same orbital angular momentum. The exchange interaction is produced by only a neutral meson. The involving mesons without electric charge that it gives exchange forces between protons and Neutrons. Also therefore maintains charge independence character. It is evident for the nature of the products that neutral mesons decay by both strong and weak interactions. It means that neutral mesons’ constituents are responsible for the electromagnetic interaction. Dramatically neutral mesons play an important role for both electromagnetic and nuclear forces. [ABSTRACT FROM AUTHOR]

A quark-meson-diquark plasma is considered within the Polyakov-loop extended Nambu-Jona-Lasinio model for dynamical chiral symmetry breaking and restoration in quark matter. Based on a generalized Beth-Uhlenbeck approach to mesons and diquarks we present the thermodynamics of this system including the Mott dissociation of mesons and diquarks at finite temperature. A striking result is the suppression of the diquark abundance below the chiral restoration temperature by the coupling to the Polyakov loop, because of their color degree of freedom. This is understood in close analogy to the suppression of quark distributions by the same mechanism. Mesons as color singlets are unaffected by the Polyakov-loop suppression. At temperatures above the chiral restoration mesons and diquarks are both suppressed due to the Mott effect, whereby the positive resonance contribution to the pressure is largely compensated by the negative scattering contribution in accordance with the Levinson theorem. [ABSTRACT FROM AUTHOR]

Recently, a new symmetry of mesons has been found upon truncation of the quasizero modes of the overlap Dirac operator in lattice simulations. Namely, the ρ, ρ', ω, ω', a1, b1, h1, and possibly f1 J=1 mesons get degenerate after removal of the quasizero modes. This emergent symmetry has been established to be SU(4)⊃SU(2)L×SU(2)R×U(1)A. It is higher than the symmetry of the QCD Lagrangian and provides not only a mixing of quarks of given chirality in the isospin space, but also the mixing of left-handed and right-handed components. Here we study, with the overlap Dirac operator, the isovector J=2 mesons upon the quasizero mode reduction and observe a similar degeneracy. This result further supports the SU(4) symmetry in mesons of given spin J=1. [ABSTRACT FROM AUTHOR]

We present a first look at the spectroscopy of SU(4) gauge theory coupled to two flavors of Dirac fermions in the two-index antisymmetric representation, which is a real representation. We compute meson and diquark masses, the pseudoscalar and vector meson decay constants, and the masses of six-quark baryons. We make comparisons with large-Nc expectations. [ABSTRACT FROM AUTHOR]

We explore the use of "optimized" operators, designed to interpolate only a single meson eigenstate, in three-point correlation functions with a vector-current insertion. These operators are constructed as linear combinations in a large basis of meson interpolating fields using a variational analysis of matrices of two-point correlation functions. After performing such a determination at both zero and nonzero momentum, we compute three-point functions and are able to study radiative transition matrix elements featuring excited-state mesons. The required two- and three-point correlation functions are efficiently computed using the distillation framework in which there is a factorization between quark propagation and operator construction, allowing for a large number of meson operators of definite momentum to be considered. We illustrate the method with a calculation using anisotopic lattices having three flavors of dynamical quark all tuned to the physical strange quark mass, considering form factors and transitions of pseudoscalar and vector meson excitations. The dependence on photon virtuality for a number of form factors and transitions is extracted, and some discussion of excited-state phenomenology is presented. [ABSTRACT FROM AUTHOR]