Search Results (481)

I review possible signals at hadron colliders of bileptons, namely doubly charged vectors or scalars with lepton number $L=\pm 2$, as predicted by a 331 model, based on a $SU{\left(3\right)}_c\times SU{\left(3\right)}_L\times U{\left(1\right)}_X$ symmetry. In particular, I account for a version of the 331 model wherein the embedding of the hypercharge is obtained with the addition of three exotic quarks and vector bileptons. Furthermore, a sextet of $SU{\left(3\right)}_L$, necessary to provide masses to leptons, yields an extra scalar sector, including a doubly charged Higgs, i.e., scalar bileptons. As bileptons are mostly produced in pairs at hadron colliders, their main signal is provided by two same-sign lepton pairs at high invariant mass. Nevertheless, they can also decay according to non-leptonic modes, such as a TeV-scale heavy quark, charged 4/3 or 5/3, plus a Standard Model quark. I explore both leptonic and non-leptonic decays and the sensitivity to the processes of the present and future hadron colliders. Full article

The effective baryon–baryon potential can be derived in the framework of the quark model. The configurations with different quark spatial distributions are mixed naturally when two baryons get close. The effect of configuration mixing in the chiral quark model (ChQM) is studied by calculating the effective potential between two non-strange baryons in the channels $IJ=01,10$ and 03. For comparison, the results of the color screening model (CSM) are also presented. Generally, configuration mixing will lower the potential when the separation between two baryons is small, and its effect will be ignorable when the separation becomes large. Due to the screened color confinement, the effect of configuration mixing is rather large, which leads to stronger intermediate-range attraction in the CSM, while the effect of configuration mixing is small in the ChQM due to the quadratic confinement and $\sigma$-meson exchange, which is responsible for the intermediate-range attraction. Full article

The lack of positive evidence for Weakly Interacting Massive Particles (WIMPs) as well as the lack of discovery of supersymmetric (SUSY) particles at the LHC may appeal to a non-supersymmetric solution for the Standard Model problem of the Higgs boson mass divergence, the origin of the electroweak energy scale and the physical nature of the cosmological dark matter in the approach of composite Higgs boson. If the Higgs boson consists of charged constituents, their binding can lead to stable particles with electroweak charges. Such particles can take part in sphaleron transitions in the early Universe, which balance their excess with baryon asymmetry. Constraints on exotic charged species leave only stable particles with charge $-2n$ possible, which can bind with n nuclei of primordial helium in neutral dark atoms. The predicted ratio of densities of dark atoms and baryonic matter determines the condition for dark atoms to dominate in the cosmological dark matter. To satisfy this condition of the dark-atom nature of the observed dark matter, the mass of new stable $-2n$ charged particles should be within reach of the LHC for their searches. We discuss the possibilities of dark-atom binding in multi-atom systems and present state-of-the-art quantum mechanical descriptions of dark-atom interactions with nuclei. Annual modulations in such interactions with nuclei of underground detectors can explain the positive results of DAMA/NaI and DAMA/LIBRA experiments and the negative results of the underground WIMP searches. Full article

In the absence of a Grand Unified Theory framework, connecting the values of the mixing parameters in the quark-and-lepton sector is a difficult task, unless one introduces ad hoc relations among the matrices that diagonalize such different kinds of fermions. In this paper, we discuss in detail the possibility that the PMNS matrix is given by the product $U_{PMNS}=V_{CKM}^{★}{T}^{★}$, where T comes from the diagonalization of a see-saw like mass matrix that can be of a Bimaximal (BM), Tri-Bimaximal (TBM) and Golden Ratio (GR) form, and identify the leading corrections to such patterns that allow for a good fit to the leptonic mixing matrix as well as to the CP phase. We also show that the modified versions of BM, TBM and GR can easily accommodate the solar and atmospheric mass differences. Full article

We present a study of hybrid neutron stars with color superconducting quark matter cores at a finite temperature that results in sequences of stars with constant entropy per baryon, $s/n_B=\mathrm{const}$. For the quark matter equation of state, we employ a recently developed nonlocal chiral quark model, while nuclear matter is described with a relativistic density functional model of the DD2 class. The phase transition is obtained through a Maxwell construction under isothermal conditions. We find that traversing the mixed phase on a trajectory at low $s/n_B\lesssim 2$ in the phase diagram shows a heating effect, while at larger $s/n_B$ the temperature drops. This behavior may be attributed to the presence of a color superconducting quark matter phase at low temperatures and the melting of the diquark condensate which restores the normal quark matter phase at higher temperatures. While the isentropic hybrid star branch at low $s/n_B\lesssim 2$ is connected to the neutron star branch, it becomes disconnected at higher entropy per baryon so that the “thermal twin” phenomenon is observed. We find that the transition from connected to disconnected hybrid star sequences may be estimated with the Seidov criterion for the difference in energy densities. The radii and masses at the onset of deconfinement exhibit a linear relationship and thus define a critical compactness of the isentropic star configuration for which the transition occurs and which, for large enough $s/n_B\gtrsim 2$ values, is accompanied by instability. The results of this study may be of relevance for uncovering the conditions for the supernova explodability of massive blue supergiant stars using the quark deconfinement mechanism. The accretion-induced deconfinement transition with thermal twin formation may contribute to explaining the origin of eccentric orbits in some binary systems and the origin of isolated millisecond pulsars. Full article

Quark–Gluon plasma driven by the strong force is subject to the conservativeness of the baryon number, net electric charge, strangeness, etc. However, the fluctuations around their mean values at specific temperatures and chemical potentials can provide viable signals for the production of Quark–Gluon plasma. These fluctuations can be captured theoretically as moments of different orders in the expansion of pressure or the thermodynamic potential of the system under concern. Here, we look for possible explanations in the methodologies used for capturing them by using the framework of the Polyakov–Nambu–Jona-Lasinio (PNJL) model under the 2 + 1 flavor consideration with mean-field approximation. The various quantities thus explored can act to signify meaningfully near the phase transitions. Justifications are also made for some of the quantities capable of serving necessarily under experimental scenarios. Additionally, variations in certain quantities are also made for the different collision energies explored in the high-energy experiments. Rectification of the quantitative accuracy, especially in the low-temperature hadronic sector, is of prime concern, and it is also addressed. It was found that most of the observables stay in close proximity with the existing lattice QCD results at the continuum limit, with some artifacts still remaining, especially in the strange sector, which needs further attention. Full article

Feline calicivirus (FCV), an important model for studying the biology of the Caliciviridae family, encodes the leader of the capsid (LC) protein, a viral factor known to induce apoptosis when expressed in a virus-free system. Our research has shown that the FCV LC protein forms disulfide bond-dependent homo-oligomers and exhibits intrinsic toxicity; however, it lacked a polybasic region and a transmembrane domain (TMD); thus, it was initially classified as a non-classical viroporin. The unique nature of the FCV LC protein, with no similarity to other proteins beyond the Vesivirus genus, has posed challenges for bioinformatic analysis reliant on sequence similarity. In this study, we continued characterizing the LC protein using the AlphaFold 2 and the recently released AlphaFold 3 artificial intelligence tools to predict the LC protein tertiary structure. We compared it to other molecular modeling algorithms, such as I-Tasser’s QUARK, offering new insights into its putative TMD. Through exogenous interaction, we found that the recombinant LC protein associates with the CrFK plasmatic membrane and can permeate cell membranes in a disulfide bond-independent manner, suggesting that this interaction might occur through a TMD. Additionally, we examined its potential to activate the intrinsic apoptosis pathway in murine and human ovarian cancer cell lines, overexpressing survivin, an anti-apoptotic protein. All these results enhance our understanding of the LC protein’s mechanism of action and suggest its role as a class-I viroporin. Full article

Convenient and consistent phase convention is important in the construction of the hadronic Lagrangian. However, the importance of phase convention has been overlooked for a long time, and the sources of different conventions are never explicitly addressed. This obscure situation can cause mistakes and misinterpretations in hadron physics. In this paper, we systematically analyze and compare the flavor $S{U}_3$ phase conventions from the perspective of the quark model. All sources that could lead to different conventions are pointed out and carefully studied. With the tool of the quark model, we also clarify some misconceptions and demonstrate a consistent way to incorporate different conventions. Full article

The concept of symmetry under various transformations of quantities describing basic natural phenomena is one of the fundamental principles in the mathematical formulation of physical laws. Starting with Noether’s theorems, we highlight some well–known examples of global symmetries and symmetry breaking on the particle level, such as the separation of strong and electroweak interactions and the Higgs mechanism, which gives mass to leptons and quarks. The relation between symmetry energy and charge symmetry breaking at both the nuclear level (under the interchange of protons and neutrons) and the particle level (under the interchange of u and d quarks) forms the main subject of this work. We trace the concept of symmetry energy from its introduction in the simple semi-empirical mass formula and liquid drop models to the most sophisticated non-relativistic, relativistic, and ab initio models. Methods used to extract symmetry energy attributes, utilizing the most significant combined terrestrial and astrophysical data and theoretical predictions, are reviewed. This includes properties of finite nuclei, heavy-ion collisions, neutron stars, gravitational waves, and parity–violating electron scattering experiments such as CREX and PREX, for which selected examples are provided. Finally, future approaches to investigation of the symmetry energy and its properties are discussed. Full article

We study the strong decays of the $\varphi \left(2170\right)$, along with its possible partner $X\left(2436\right)$, as two fully strange tetraquark states of $J^{PC}=1^{--}$. These two states are assumed to contain two strange quarks and two anti-strange quarks, with the flavor symmetry ${\mathbf{6}}_{ss}\otimes {\overline{\mathbf{6}}}_{\overline{s}\overline{s}}$. We consider seven decay channels: $\varphi \eta$, $\varphi {\eta }^{\prime }$, $\varphi f_0\left(980\right)$, $\varphi f_1\left(1420\right)$, $h_1\left(1415\right)\eta$, $h_1\left(1415\right){\eta }^{\prime }$, and $h_1\left(1415\right)f_1\left(1420\right)$. Some of these channels are kinematically possible, and we calculate their relative branching ratios through the Fierz rearrangement. Future experimental measurements on these ratios could be useful in determining the nature of the $\varphi \left(2170\right)$ and $X\left(2436\right)$. The $\varphi \left(2170\right)$ has been observed in the $\varphi f_0\left(980\right)$, $\varphi \eta$, and $\varphi {\eta }^{\prime }$ channels, and we propose to further examine it in the $h_1\left(1415\right)\eta$ channel. Evidences of the $X\left(2436\right)$ have been observed in the $\varphi f_0\left(980\right)$ channel, and we propose to verify whether this structure exists or not in the $\varphi \eta$, $\varphi {\eta }^{\prime }$, $h_1\left(1415\right)\eta$, and $h_1\left(1415\right){\eta }^{\prime }$ channels. Full article

White dwarfs are the remnants of stars not massive enough to become supernovae. This review explores the concept of strange dwarfs, a unique class of white dwarfs that contain cores of strange quark matter. Strange dwarfs have different sizes, masses, and evolutionary paths with respect to white dwarfs. They might form through the accumulation of normal matter on strange quark stars or by the capture of strangelets. The stability of strange dwarfs has been debated, with initial studies suggesting stability, while later analyses indicated potential instability. This review revisits these discussions, focusing on the critical role of boundary conditions between nuclear and quark matter in determining stability. It also offers insights into their formation, structure, and possible detection in the universe. Full article

SQM-ISS is a detector that will search from the International Space Station for massive particles possibly present among the cosmic rays. Among them, we mention strange quark matter, Q-Balls, lumps of fermionic exotic compact stars, Primordial Black Holes, mirror matter, Fermi balls, etc. These compact, dense objects would be much heavier than normal nuclei, have velocities of galaxy-bound systems, and would be deeply penetrating. The detector is based on a stack of scintillator and piezoelectric elements which can provide information on both the charge state and mass, with the additional timing information allowing to determine the speed of the particle, searching for particles with velocities of the order of galactic rotation speed (v ≲ 250 km/s). In this work, we describe the apparatus and its observational capabilities. Full article

We review and meta-analyze particle data and properties of hadrons with measured rest masses. The results of our study are summarized as follows. (1) The strong-force suppression of the repulsive Coulomb forces between quarks is sufficient to explain the differences between mass deficits in nucleons and pions (and only them), the ground states with the longest known mean lifetimes; (2) unlike mass deficits, the excitations in rest masses of all particle groups are effectively quantized, but the rules are different in baryons and mesons; (3) the strong field is aware of the extra factor of ${\vartheta }_{\mathrm{e}}=2$ in the charges (Q) of the positively charged quarks; (4) mass deficits incorporate contributions proportional to the mass of each valence quark; (5) the scaling factor of these contributions is the same for each quark in each group of particles, provided that the factor ${\vartheta }_{\mathrm{e}}=2$ is taken into account; (6) besides hypercharge (Y), the much lesser-known “strong charge” ($Q^{\prime }=Y-Q$) is very useful in SU(3) in describing properties of particles located along the right-leaning sides and diagonals of the weight diagrams; (7) strong decays in which $Q^{\prime }$ is conserved are differentiated from weak decays, even for the same particle; and (8) the energy diagrams of (anti)quark transitions indicate the origin of CP violation. Full article

Since its discovery in the 1960s, the violation of CP symmetry has intrigued scientists and stimulated the advancement of knowledge in particle physics. Numerous experiments were designed and built to study it in increasingly deeper detail. Nowadays, the phenomenon is well framed within the Standard Model of Particle Physics. Nevertheless, new results are being produced by modern experiments at colliders that challenge the current understanding of the model. In this article, the current status of CP violation studies and the role of CP violation in the search for effects beyond the Standard Model are described together with the prospects for ongoing and future experiments. Full article

We estimate the magnetic moment of electron neutrinos by computing the neutrino chirality flip rate that can occur in the core of a strange quark matter neutron star at birth. We show that this process allows neutrinos to anisotropically escape, thus inducing the star kick velocity. Although the flip from left- to right-handed neutrinos is assumed to happen in equilibrium, the no-go theorem does not apply because right-handed neutrinos do not interact with matter and the reverse process does not happen, producing the loss of detailed balance. For simplicity, we model the star core as consisting of strange quark matter. We find that even when the energy released in right-handed neutrinos is a small fraction of the total energy released in left-handed neutrinos, the process describes kick velocities for natal conditions, which are consistent with the observed ones and span the correct range of radii, temperatures and chemical potentials for typical magnetic field intensities. The neutrino magnetic moment is estimated to be ${\mu }_{\nu }\sim 3.6\times {10}^{-18}{\mu }_B$, where ${\mu }_B$ is the Bohr magneton. This value is more stringent than the bound found for massive neutrinos in a minimal extension of the standard model. Full article