Recently the ATLAS Collaboration at CERN reported on the measurement of the branching ratio $R_{{\mathrm{\Lambda }}_b}=\mathrm{\Gamma }({\mathrm{\Lambda }}_b^0\to \psi (2S){\mathrm{\Lambda }}^0)/\mathrm{\Gamma }({\mathrm{\Lambda }}_b^0\to J/\psi {\mathrm{\Lambda }}^0)$. The measured branching ratio $R_{{\mathrm{\Lambda }}_b}=0.501\pm 0.033(\text{stat})\pm 0.019(\text{syst})$ was found to be lower than the covariant quark model prediction of $R_{{\mathrm{\Lambda }}_b}=0.8\pm 0.1$ calculated by us recently. We present a detailed analysis of the branching ratio $R_{{\mathrm{\Lambda }}_b}$ using a model-independent framework for the heavy-to-light form factors based on results from our previous papers.

We study the $P$-wave bottom baryons using the method of QCD sum rule and heavy quark effective theory. Our results suggest that ${\mathrm{\Lambda }}_b(5912{)}^0$ and ${\mathrm{\Lambda }}_b(5920{)}^0$ can be well described by the baryon doublet $[{\overline{\mathbf{3}}}_F,1,1,\rho ]$, and they belong to the $SU(3)$ ${\overline{\mathbf{3}}}_F$ multiplets of $J^P=1/2^{-}$ and $3/2^{-}$. Their $SU(3)$ flavor partners, ${\mathrm{\Xi }}_b(1/2^{-})$ and ${\mathrm{\Xi }}_b(3/2^{-})$, have masses $6.06\pm 0.13\mathrm{GeV}$ and $6.07\pm 0.13\mathrm{GeV}$, respectively, with mass splitting $9\pm 4\mathrm{MeV}$. The results obtained using baryon doublet $[{\overline{\mathbf{3}}}_F,1,0,\lambda ]$ are similar and also consistent with the experimental data. We also study the $SU(3)$ ${\mathbf{6}}_F$ multiplets by using the baryon multiplets $[{\mathbf{6}}_F,0,1,\lambda ]$, $[{\mathbf{6}}_F,1,0,\rho ]$ and $[{\mathbf{6}}_F,2,1,\lambda ]$, and our results suggest that the $P$-wave bottom baryons ${\mathrm{\Sigma }}_b$, ${\mathrm{\Xi }}_b^{\prime }$ and ${\mathrm{\Omega }}_b$ have (averaged) masses of about 6.0 GeV, 6.2 GeV and 6.4 GeV, respectively.

Observed enhancements in the forward and backward directions for $\varphi$-meson photoproduction off nucleons are shown to be explainable by the production of a nonresonant recoiling $(su)$ diquark, $(\overline{s}ud)$ triquark pair. We show that the necessity of maintaining approximate collinearity of the quarks within these units constrains configurations with the minimum momentum transfer, and hence maximal amplitudes, to lie preferentially along the reaction axis.

A major experimental program is presently underway worldwide to determine the fundamental nonperturbative functions, the Sivers, Boer-Mulders and transversity distributions, which are vital for an understanding of the internal structure of the nucleon. However, at present, many simplifying assumptions are used in extracting these functions from the data. We demonstrate that if the binning of the data in $Q^2$ is small enough so that $Q^2$ evolution can be neglected inside a bin, then one can obtain stringent tests of these assumptions. Failure to satisfy these tests implies that the presently extracted nonperturbative functions are unreliable. To this end, we consider the measurement of the Sivers, Boer-Mulders and transversity difference asymmetries for hadrons with opposite charges in SIDIS reactions with unpolarized and transversely polarized deuteron and proton targets: $l+N\to l^{\prime }+h+X$, $h={\pi }^{\pm }$, $K^{\pm }$, $h^{\pm }$. Utilizing only charge and isospin invariance, and applying the above mentioned simplifying assumptions, we obtain several testable relations amongst the measured asymmetries. If these tests are satisfied, then the measured asymmetries determine two different combinations of the valence-quark transverse-momentum-dependent distributions, which can be determined separately without any contributions from the strange and other sea quarks.

The effect of the pion exchange on the line shape of near threshold bottomoniumlike resonances decaying into an $S$ wave pair of $B^{(*)}$ mesons is considered. It is pointed out that this effect, parametrically enhanced by the heavy meson mass, can be of a practical significance in determining the parameters of the bottomoniumlike resonances such as the known $Z_b(10610)$ and $Z_b(10650)$ states.

Inspired by the recent findings of the two $P_c^{+}$ states in the $J/\psi p$ mass spectrum at LHCb, we investigate the elastic and inelastic cross sections of the $J/\psi N$, ${\eta }_{c}N$, $\mathrm{\Upsilon }N$ and ${\eta }_{b}N$ channels within the constraints from heavy quark spin and flavor symmetry. The ${\overline{D}}^{(*)}{\mathrm{\Sigma }}_c^{(*)}$ ($B^{(*)}{\mathrm{\Sigma }}_b^{(*)}$) bound states predicted in earlier works should be accessible in elastic and/or inelastic processes of the $J/\psi N$ and/or ${\eta }_{c}N$ ($\mathrm{\Upsilon }N$ and/or ${\eta }_{b}N$) interactions.

We have searched for a short-range spin-dependent interaction using the spin relaxation of hyperpolarized ${}^3\mathrm{He}$. Such a new interaction would be mediated by a hypothetical light scalar boson with $CP$-violating couplings to the neutron. The walls of the ${}^3\mathrm{He}$ cell would generate a pseudomagnetic field and induce an extra depolarization channel. We did not see any anomalous spin relaxation, and we report the limit for interaction ranges $\lambda$ between 1 and $100\mu \mathrm{m}$, $g_s{g}_p{\lambda }^2\le 2.6\times 10^{-28}{\mathrm{m}}^2$ (95% C.L.), where $g_s(g_p)$ are the (pseudo)scalar coupling constant, improving the previous best limit by 1 order of magnitude.

In this paper, we put forward a special neutrino mass matrix which is invariant under a modified Friedberg-Lee (FL) transformation ${\nu }_e\to {\nu }_e-2\xi$ and ${\nu }_{\mu ,\tau }\to {\nu }_{\mu ,\tau }+\xi$ with $\xi$ being a space-time independent element of the Grassmann algebra. Compared to the original FL symmetry (with the transformation ${\nu }_{e,\mu ,\tau }\to {\nu }_{e,\mu ,\tau }+\xi$) which results in the TM2 neutrino mixing, the modified FL symmetry will lead us to the TM1 mixing which has a better agreement with the experimental results. While the original FL symmetry has to be broken in order to produce a realistic neutrino mass spectrum, the modified FL symmetry is allowed to remain intact and give us a vanishing $m_1$. A combination of the FL symmetry with the $\mu -\tau$ reflection symmetry is also discussed.

The per-event yield of the highest transverse momentum charged particle and charged-particle jet, integrated above a given $p_{\mathrm{T}}^{\min }$ threshold starting at $p_{\mathrm{T}}^{\min }=0.8$ and 1 GeV, respectively, is studied in $pp$ collisions at $\sqrt{s}=8\mathrm{TeV}$. The particles and the jets are measured in the pseudorapidity ranges $|\eta |<2.4$ and 1.9, respectively. The data are sensitive to the momentum scale at which parton densities saturate in the proton, to multiple partonic interactions, and to other key aspects of the transition between the soft and hard QCD regimes in hadronic collisions.

We study the dynamics of light quantum scalar fields in de Sitter space on superhorizon scales. We compute the self-energy of an $O(N)$ symmetric theory at next-to-leading order in a $1/N$ expansion in the regime of superhorizon momenta, and we obtain an exact analytical solution of the corresponding Dyson-Schwinger equations for the two-point correlator. This amounts to resumming the infinite series of nonlocal self-energy insertions, which typically generate spurious infrared and/or secular divergences. The potentially large de Sitter logarithms resum into well-behaved power laws from which we extract the field strength and mass renormalization. The nonperturbative $1/N$ expansion allows us to discuss the case of vanishing and negative tree-level square mass, which both correspond to strongly coupled effective theories in the infrared.

We study a scalar-tensor version of Lovelock theory with a nontrivial higher-order Galileon term involving the coupling of the Lovelock two tensor with derivatives of the scalar Galileon field. For a static and spherically symmetric spacetime, we extend the Boulware-Deser solution to the presence of a Galileon field. The hairy solution has a regular scalar field on the black hole event horizon and presents certain self-tuning properties for the bulk cosmological constant and the Gauss-Bonnet coupling. The combined time and radial dependence of the Galileon field permits its horizon regularity. Furthermore in order to investigate the effects of linear time dependence we find spherically symmetric solutions in four and five spacetime dimensions. They are shown to have singular horizons. Afar from the Schwarzschild radius and for weak higher-dimensional couplings the solutions are perturbatively close to GR representing exteriors of GR-like star solutions for scalar tensor theories.

Einstein-Maxwell theory conformally coupled to a scalar field in $D$ dimensions may exhibit a phase transition at low temperature whose end point is an asymptotically anti–de Sitter black hole with a scalar field profile that is regular everywhere outside and on the horizon. This provides a tractable model to study the phase transition of hairy black holes in anti–de Sitter space in which the backreaction on the geometry can be solved analytically.

An interaction between the vacuum energy and dark matter is an intriguing possibility which may offer a way of solving the cosmological constant problem. Adopting a general prescription for momentum exchange between the two dark components, we reconstruct $\alpha (a)$, the temporal evolution of the coupling strength between dark matter and vacuum energy, in a nonparametric Bayesian approach using combined observational data sets from the cosmic microwave background, supernovae and large scale structure. An evolving interaction between the vacuum energy and dark matter removes some of the tensions between different data sets. However, it is not preferred over $\mathrm{\Lambda }\mathrm{CDM}$ in the Bayesian sense, as improvement in the fit is not sufficient to compensate for the increase in the volume of the parameter space.

Inflation has long been considered the best way to produce primordial large-scale magnetic fields. To achieve fields strong enough to seed the galactic dynamo, most of the mechanisms operate outside conventional electromagnetic theory. The latter is typically restored after the end of the de Sitter phase. Breaking away from standard electromagnetism can lead to substantially stronger magnetic fields by the end of inflation, thus compensating for their subsequent adiabatic depletion. We argue that the drastic magnetic enhancement during the de Sitter era may no longer be necessary because, contrary to the widespread perception, superhorizon-sized magnetic fields decay at a slower pace after inflation. The principle behind this claim is causality, which confines the postinflationary electric currents inside the horizon. Without the currents there can be no magnetic-flux freezing on super-Hubble lengths. There, the magnetic decay rate slows down, thus making it much easier to produce primordial fields of astrophysical interest. To quantify this qualitative statement, one can start from the current galactic-dynamo requirements and “reverse engineer” the magnetic strengths needed at the end of inflation in order to produce astrophysically relevant residual seeds today. Our numerical estimates suggest that, depending on the magnetic scale, mechanisms of inflationary magnetogenesis generating fields stronger than ${10}^{17}\mathrm{G}$ by the end of the de Sitter phase could successfully seed the galactic dynamo at present.

The scattering of sub-GeV dark matter (DM) particles with hydrogen atoms is studied in this paper. The interactions of DM with electrons and nucleons are both included and formulated in a general framework based on nonrelativistic effective field theory. On the assumption of the same dark matter coupling strengths, it is found that DM-electron interactions dominate the inelastic atomic transitions to discrete excited states and ionization continuum around the threshold regions, and DM-nucleon interactions become more important with increasing energy and dominate in elastic scattering. The conclusion should apply, qualitatively, to practical detector species so that electronic and nuclear contributions in DM scattering processes can be disentangled, while issues including binding effects and the recoil mechanism in many-body systems will require further detailed calculations.

We consider monojet searches at the Large Hadron Collider (LHC) for spin-1 dark matter that interacts with quarks through a contact operator. If the dark matter particles are produced with longitudinal polarizations, then the production matrix element is enhanced by factors of the energy. We show that this particularly effective search strategy can test models for which the energy suppression scale of the operator is as large as ${10}^5\mathrm{TeV}$. As such, these searches can probe a large class of models for which the contact-operator approximation is valid. We find that for contact operators that permit velocity-independent dark matter–nucleon scattering, LHC monojet searches for spin-1 dark matter are competitive with or far surpass direct-detection searches depending on whether the scattering is spin independent or spin dependent, respectively.

In this work I present a complete analysis of proton decay in an $SO(10)$ model previously proposed by Dutta, Mimura, and Mohapatra. The $\mathbf{10}$, $\overline{\mathbf{126}}$, and $\mathbf{120}$ Yukawa couplings contributing to fermion masses in this model have well-motivated restrictions on their textures intended to give favorable results for proton lifetime as well as a realistic fermion sector without the need for fine-tuning and for either type-I or type-II dominance in the neutrino mass matrix. I obtain a valid fit for the entire fermion sector for both types of seesaw dominance, including ${\theta }_{13}$ in good agreement with the most recent data. For the case with type-II seesaw, I find that using the Yukawa couplings fixed by the successful fermion sector fit, proton partial lifetime limits are satisfied for nearly every pertinent decay mode, even for nearly arbitrary values of the triplet Higgs mixing parameters, with only the $K^{+}\overline{\nu }$ mode requiring a minor $\mathcal{O}(10^{-1})$ cancellation in order to satisfy the experimental limit. I also find a maximum lifetime for that mode of $\tau (K^{+}\overline{\nu })\sim {10}^{36}\mathrm{yr}$, which should be tested by forthcoming experiments. For the type-I seesaw case, I find that all six pertinent decay modes of interest are satisfied for values of the triplet mixing parameters giving no major enhancement, with modes other than $K^{+}\overline{\nu }$ easily satisfied for arbitrary mixing values, and with a maximum lifetime for $K^{+}\overline{\nu }$ of nearly ${10}^{38}\mathrm{yr}$.

We perform a detailed analysis of the two-Higgs doublet model (2HDM) potential. At the tree level, the potential may accommodate more than one minima, one of them being the electroweak (EW) minimum where the Universe lives. The parameter space allowed after the data from the Large Hadron Collider (LHC) came in almost excludes those cases where the EW vacuum is shallower than the second minimum. We extend the analysis by including terms in the 2HDM potential that break the $Z_2$ symmetry of the potential by dimension-4 operators and show that the conclusions remain unchanged. Furthermore, a one-loop analysis of the potential is performed for both cases, namely, where the $Z_2$ symmetry of the potential is broken by dimension-2 or dimension-4 operators. For quantitative analysis, we show our results for the type II 2HDM, qualitative results remaining the same for other 2HDMs. We find that the nature of the vacua from the tree-level analysis does not change; the EW vacuum still remains deeper.

We propose a new method to calculate electric dipole moments induced by the strong QCD $\theta$ term. The method is based on the gradient flow for gauge fields and is free from renormalization ambiguities. We test our method by computing the nucleon electric dipole moments in pure Yang-Mills theory at several lattice spacings, enabling a first-of-its-kind continuum extrapolation. The method is rather general and can be applied for any quantity computed in a $\theta$ vacuum. This first application of the gradient flow has been successful and demonstrates proof-of-principle, thereby providing a novel method to obtain precise results for nucleon and light nuclear electric dipole moments.