We study perturbative unitarity in a Lorentz-symmetry-violating QED model with higher-order derivative operators in the light of the results of Lee and Wick to preserve unitarity in indefinite metric theories. Specifically, we consider the fermionic sector of the Myers-Pospelov model, which includes dimension-five operators, coupled to standard photons. We canonically quantize the model, paying attention to its effective character, and show that its Hamiltonian is stable, emphasizing the exact stage at which the indefinite metric appears and decomposes into a positive-metric sector and a negative-metric sector. Finally, we verify the optical theorem at the one-loop level in the annihilation channel of the forward-scattering process $e^{+}(p_2,r)+e^{-}(p_1,s)$ by applying the Lee-Wick prescription, in which the states associated with the negative metric are left out from the asymptotic Hilbert space, but nevertheless are considered in the loop integration via the propagator.

The observation of a charged-lepton flavor violating process would be a definite sign for physics beyond the Standard Model, but would actually only prove that one particular linear combination of lepton numbers is violated. We categorize lepton-flavor-violating processes by their quantum numbers and show how their discovery can be interpreted model independently, studying in particular which processes are required to establish that the entire flavor group is broken. We also comment on total lepton number, seeing as lepton number violation practically implies lepton flavor violation as well.

We analyze, within a dipole model, the final, inclusive HERA DIS cross section data in the low $x$ region, using fully correlated errors. We show that these highest precision data are very well described within the dipole model framework starting from $Q^2$ values of $3.5{\mathrm{GeV}}^2$ to the highest values of $Q^2=250{\mathrm{GeV}}^2$. To analyze the saturation effects we evaluated the data including also the very low $0.35<Q^2{\mathrm{GeV}}^2$ region. The fits including this region show a preference of the saturation ansatz.

A search for supersymmetry is performed in events with a single electron or muon in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were recorded by the CMS experiment at the LHC and correspond to an integrated luminosity of $2.3{\mathrm{fb}}^{-1}$. Several exclusive search regions are defined based on the number of jets and $b$-tagged jets, the scalar sum of the jet transverse momenta, and the scalar sum of the missing transverse momentum and the transverse momentum of the lepton. The observed event yields in data are consistent with the expected backgrounds from standard model processes. The results are interpreted using two simplified models of supersymmetric particle spectra, both of which describe gluino pair production. In the first model, each gluino decays via a three-body process to top quarks and a neutralino, which is associated with the observed missing transverse momentum in the event. Gluinos with masses up to 1.6 TeV are excluded for neutralino masses below 600 GeV. In the second model, each gluino decays via a three-body process to two light quarks and a chargino, which subsequently decays to a $W$ boson and a neutralino. The mass of the chargino is taken to be midway between the gluino and neutralino masses. In this model, gluinos with masses below 1.4 TeV are excluded for neutralino masses below 700 GeV.

We develop computational tools for calculating supersymmetric higher-order derivative corrections to eleven-dimensional supergravity using the action principle approach. We show that, provided the superspace Bianchi identities admit a perturbative solution in the derivative expansion, there are at least two independent superinvariants at the eight-derivative order of eleven-dimensional supergravity. Assuming the twelve superforms associated to certain anomalous Chern-Simons terms are Weil trivial, there will be a third independent superinvariant at this order. Under certain conditions, at least two superinvariants will survive to all orders in the derivative expansion. However only one of them will be present in the quantum theory: the supersymmetrization of the Chern-Simons terms of eleven-dimensional supergravity required for the cancellation of the M5-brane gravitational anomaly by inflow. This superinvariant can be shown to be unique at the eight-derivative order, assuming it is quartic in the fields. On the other hand, a necessary condition for the superinvariant to be quartic is the exactness, in $\tau$-cohomology, of $X_{0,8}$, the purely spinorial component of the eight superform related by descent to the M5-brane anomaly polynomial. In that case it can also be shown that the solution of the Weil-triviality condition of the corresponding twelve form, which is a prerequisite for the explicit construction of the superinvariant, is guaranteed to exist. We prove that certain highly nontrivial necessary conditions for the $\tau$-exactness of $X_{0,8}$ are satisfied. Moreover any potential superinvariant associated to anomalous Chern-Simons terms at the eight-derivative order must necessarily contain terms cubic or lower in the fields.

We explore the warm inflation scenario theoretical predictions looking at two different dissipative regimes for several representative primordial potentials. As it is well known, warm inflation is able to decrease the tensor-to-scalar ratio value, rehabilitating several primordial potentials ruled out in the cold inflation context by the recent cosmic microwave background data. Here we show that warm inflation is also able to produce a running of the running ${\beta }_s$ positive and within the Planck data limits. This is very remarkable since the standard cold inflation model is unable to justify the current indication of a positive constraint on ${\beta }_s$. We achieve a parametrization for the primordial power spectrum able to take into account higher order effects as the running of the spectral index and the running of the running, and we perform statistical analysis using the most up-to-date Planck data to constrain the dissipative effects. We find that the warm inflation can explain the current observables with a good statistical significance, even for those potentials ruled out in the simplest cold inflation scenario.

The Fokker-Planck (FP) equation ${\partial }_{t}f+\mu {\partial }_{x}f={\partial }_{\mu }(1-{\mu }^2){\partial }_{\mu }f$ is solved analytically. Foremost among its applications, this equation describes the propagation of energetic particles through a scattering medium (in $x$- direction, with $\mu$ being the $x$- projection of particle velocity). The solution is found in terms of an infinite series of mixed moments of particle distribution, $⟨{\mu }^j{x}^k⟩$. The second moment $⟨x^2⟩$ ($j=0$, $k=2$) was obtained by G. I. Taylor (1920) in his classical study of random walk: $⟨x^2⟩={⟨x^2⟩}_0+t/3+[\exp (-2t)-1]/6$ (where $t$ is given in units of an average time between collisions). It characterizes a spatial dispersion of a particle cloud released at $t=0$, with $\sqrt{{⟨x^2⟩}_0}$ being its initial width. This formula distills a transition from ballistic (rectilinear) propagation phase, $⟨x^2⟩-{⟨x^2⟩}_0\approx t^2/3$ to a time-asymptotic, diffusive phase, $⟨x^2⟩-{⟨x^2⟩}_0\approx t/3$. The present paper provides all the higher moments by a recurrence formula. The full set of moments is equivalent to the full solution of the FP equation, expressed in form of an infinite series in moments $⟨{\mu }^j{x}^k⟩$. An explicit, easy-to-use approximation for a point source spreading of a pitch-angle averaged distribution $f_0(x,t)$ (starting from $f_0(x,0)=\delta (x)$, i.e., Green’s function), is also presented and verified by a numerical integration of the FP equation.

Recently, we developed an effective theory of pions and a light dilatonic meson for gauge theories with spontaneously broken chiral symmetry that are close to the conformal window. The pion mass term in this effective theory depends on an exponent $y$. We derive the transformation properties under dilatations of the renormalized fermion mass and use this to rederive $y=3-{\gamma }_m^{*}$, where ${\gamma }_m^{*}$ is the fixed-point value of the mass anomalous dimension at the sill of the conformal window. This value for $y$ is consistent with the trace anomaly of the underlying near-conformal gauge theory.

Neutrinos coming from the Sun’s core have been measured with high precision, and fundamental neutrino oscillation parameters have been determined with good accuracy. In this work, we estimate the impact that a new neutrino physics model, the so-called generalized Mikheyev-Smirnov-Wolfenstein (MSW) oscillation mechanism, has on the shape of some of leading solar neutrino spectra, some of which will be partially tested by the next generation of solar neutrino experiments. In these calculations, we use a high-precision standard solar model in good agreement with helioseismology data. We found that the neutrino spectra of the different solar nuclear reactions of the pp chains and carbon–nitrogen–oxygen cycle have quite distinct sensitivities to the new neutrino physics. The $HeP$ and ${}^{8}B$ neutrino spectra are the ones in which their shapes are more affected when neutrinos interact with quarks in addition to electrons. The shapes of the ${}^{15}O$ and ${}^{17}F$ neutrino spectra are also modified, although in these cases the impact is much smaller. Finally, the impact in the shapes of the $PP$ and ${}^{13}N$ neutrino spectra is practically negligible.

Distinctions between quark to $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ longitudinal spin transfers in the semi-inclusive deep inelastic scattering process were observed by the E665 and COMPASS Collaborations. There are suggestions that the difference between $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ production is related to the asymmetric strange-antistrange distribution inside the nucleon. However, previous calculations are still too small to explain the experimental data. From a realistic consideration of quark to $\mathrm{\Lambda }$ fragmentation due to different flavors, we investigate the strange quark contribution for $\mathrm{\Lambda }$ production and polarization. We find that the strange quark-antiquark asymmetry of the nucleon sea can be amplified into an observable quantity from the difference between $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ polarizations after taking into account the larger probability of the $\mathrm{\Lambda }$ produced from the $s$ quark fragmentation process compared to that from the $u$ or $d$ quark. The qualitative agreement between our calculation and the experimental data supports the existence of the intrinsic strange sea and the strange-antistrange asymmetry. Thus the polarization of $\mathrm{\Lambda }/\overline{\mathrm{\Lambda }}$ does open a new window to probe the nucleon sea properties, especially the strange content and its quark-antiquark asymmetry.

We study three different chiral Lagrangians that describe the two- and three-body decays of an excited pseudoscalar glueball, $J^{PC}=0^{*-+}$, into light mesons and charmonium states as well as into a scalar and pseudoscalar glueball. We compute the decay channels for an excited pseudoscalar glueball with a mass of 3.7 GeV and consider a ground-state pseudoscalar glueball of mass 2.6 GeV, following predictions from lattice QCD simulations. These states and channels are in reach of the ongoing BESIII experiment and the PANDA experiments at the upcoming FAIR facility experiment. We present the resulting decay branching ratios with a parameter-free prediction.

We present the results for the generalized transverse momentum distribution related to quark orbital angular momentum, i.e., $F_{14}$, in the MIT bag model. This model has been modified to include the Peierls-Yoccoz projection to restore translational invariance. Such a modification allows us to fulfil more satisfactorily basic sum rules that would otherwise be less elegantly carried out with the original version. Using the same model, we have calculated the twist-3 generalized parton distribution (GPD) that corresponds to orbital angular momentum à la Ji, through the Penttinen-Polyakov-Shuvaev-Strikman sum rule. Recently, a new relation between the two definitions of the quark orbital angular momentum at the density level has been proposed, which we illustrate here within the model. The sum rule is fulfilled. Still within the framework of the MIT bag model, we analyze the Wandzura-Wilczek expression for the GPD of interest. The genuine quark-gluon contribution is evaluated directly thanks to the equation of motion of the bag, which allows for a direct control of the kinematical contributions to the twist-3 GPD.

The decay mode $B\to K^{*}{\ell }^{+}{\ell }^{-}$ results in the measurement of a large number of related observables by studying the angular distribution of the decay products and is regarded as a sensitive probe of physics beyond the standard model (SM). Recently, LHCb has measured several of these observables using $3{\mathrm{fb}}^{-1}$ data, as a binned function of $q^2$, the dilepton invariant mass squared. We show how data can be used without any approximations to extract theoretical parameters describing the decay and to obtain a relation amongst observables within the SM. We find three kinds of significant disagreement between theoretical expectations and values obtained by fits. The values of the form factors obtained from experimental data show significant discrepancies when compared with theoretical expectations in several $q^2$ bins. We emphasize that this discrepancy cannot arise completely due to resonances and non-factorizable contributions from charm loops. Further, a relation between form factors expected to hold at large $q^2$ is very significantly violated. Finally, the relation between observables also indicates some deviations in the forward-backward asymmetry in the same $q^2$ regions. These discrepancies are possible evidence of physics beyond the SM.

Semileptonic $b\to c$ transitions, and in particular the ratios $R(D^{(*)})=\frac{\mathrm{\Gamma }(B\to D^{(*)}\tau \nu )}{\mathrm{\Gamma }(B\to D^{(*)}\ell \nu )}$, can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by the BABAR, Belle, and LHCb collaborations and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that $R(D)$ might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In contrast, the Standard Model prediction for $R(D^{*})$ is found to be more robust, because possible pollutions from $B^{*}$ contributions turn out to be negligibly small; this indicates that $R(D^{*})$ is a promising observable for searches of new physics.

The T2K off-axis near detector, ND280, is used to make the first differential cross section measurements of muon neutrino charged current single positive pion production on a water target at energies $\sim 0.8\mathrm{GeV}$. The differential measurements are presented as a function of the muon and pion kinematics, in the restricted phase space defined by $p_{{\pi }^{+}}>200\mathrm{MeV}/c$, $p_{\mu }>200\mathrm{MeV}/c$, $\cos ({\theta }_{{\pi }^{+}})>0.3$ and $\cos ({\theta }_{\mu })>0.3$. The total flux integrated ${\nu }_{\mu }$ charged current single positive pion production cross section on water in the restricted phase space is measured to be $⟨\sigma {⟩}_{\varphi }=4.25\pm 0.48(\mathrm{stat})\pm 1.56(\mathrm{syst})\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleon}$. The total cross section is consistent with the NEUT prediction ($5.03\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleon}$) and $2\sigma$ lower than the GENIE prediction ($7.68\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleon}$). The differential cross sections are in good agreement with the NEUT generator. The GENIE simulation reproduces well the shapes of the distributions, but overestimates the overall cross section normalization.

We propose the measurement of Drell-Yan (DY) lepton pairs in p-Pb collisions at the LHC in order to disentangle the relative contributions of leading-twist shadowing and coherent energy loss in quarkonium production off nuclei. The nuclear modification of low-mass DY production is computed at next-to-leading order using various sets of nuclear parton densities. It is then observed that shadowing effects strongly cancel out in the $J/\psi$ over DY suppression ratio $R_{\mathit{p}\mathrm{A}}^{\psi }(y)/R_{\mathit{p}\mathrm{A}}^{\mathrm{DY}}(y)$, unlike the effect of coherent energy loss. Such a measurement can be performed at forward rapidity by the ALICE and LHCb Collaborations at the LHC.

We report the result from the first search for $D^0$ decays to invisible final states. The analysis is performed on a data sample of $924{\mathrm{fb}}^{-1}$ collected at and near the $\mathrm{\Upsilon }(4S)$ and $\mathrm{\Upsilon }(5S)$ resonances with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The absolute branching fraction is determined using an inclusive $D^0$ sample, obtained by fully reconstructing the rest of the particle system including the other charmed particle. No significant signal yield is observed and an upper limit of $9.4\times {10}^{-5}$ is set on the branching fraction of $D^0$ to invisible final states at 90% confidence level.

The nonrelativistic limit of nonlocal modifications to the Klein-Gordon operator is studied, and the experimental possibilities of casting stringent constraints on the nonlocality scale via planned and/or current optomechanical experiments are discussed. Details of the perturbative analysis and semianalytical simulations leading to the dynamic evolution of a quantum harmonic oscillator in the presence of nonlocality reported in [A. Belenchia, D. M. T. Benincasa, S. Liberati, F. Marin, F. Marino, and A. Ortolan, Phys. Rev. Lett. 116, 161303 (2016)] are given, together with a comprehensive account of the experimental methodology with particular regard to sensitivity limitations related to thermal decoherence time and active cooling of the oscillator. Finally, a strategy for detecting nonlocality scales of the order of ${10}^{-22}÷{10}^{-26}\mathrm{m}$ by means of the spontaneous time-periodic squeezing of quantum-coherent states is provided.

In this work we study some properties of the non-Abelian, classically conformally invariant, three-dimensional $U(N)$ supersymmetric Chern-Simons coupled to a scalar superfield in the fundamental representation of $U(N)$, in the large $N$ limit. In leading order in $1/N$ we show that the theory has two phases: one in which it remains conformally invariant, and other where the superconformal symmetry is broken and masses for the matter fields are generated.

It is important to find nontrivial constraint relations for color-ordered amplitudes in gauge theories. In the past several years, a pure group-theoretic iterative method has been proposed for deriving linear constraints on color-ordered amplitudes in $SU(N)$ gauge theories. In this paper, we use the same method to derive linear constraints on four-point gluon amplitudes in $SO(N)$ and $Sp(2N)$ gauge theories. These constraints are derived up to four-loop order. It is found that there are $n=1$, 6, 10, 13, 16 constraint relations at $L=0$, 1, 2, 3, 4 loop orders in both $SO(N)$ and $Sp(2N)$ cases. Correspondingly, there are 2,3,5,8, and 11 independent four-point color-ordered amplitudes at $L=0$, 1, 2, 3, 4 loop orders in both theories.