We propose a Pati-Salam extension of the standard model incorporating a flavor symmetry based on the Δ(27) group. The theory realizes a realistic Froggatt-Nielsen picture of quark mixing and a predictive pattern of neutrino oscillations. We find that, for normal neutrino mass ordering, the atmospheric angle must lie in the higher octant, CP must be violated in oscillations, and there is a lower bound for the 0νββ decay rate. For the case of inverted mass ordering, we find that the lower atmospheric octant is preferred, and that CP can be conserved in oscillations. Neutrino masses arise from a low-scale seesaw mechanism, whose messengers can be produced by a Z′ portal at the LHC.
In the simplest version of a Q6 flavored supersymmetric model, we analyze the leptonic masses and mixings in the framework of a soft breaking of the μ↔τ symmetry. This breaking is controlled by the inequality meτ=meμ in the effective neutrino mass. As a consequence of this breaking, the reactor and atmospheric angle are deviate from 0∘ and 45∘, respectively. Such deviations can be enhanced or suppressed by the CP parities in the Majorana phases, so that an analytic study is carried out to remark their importance to constrain the free parameters that accommodate the mixing angles. The normal hierarchy is completely discarded in this model, the inverted hierarchy is less favored than the degenerate one where the reactor and atmospheric angles are in good agreement with the experimental data. Additionally, the model predicts defined regions for the effective neutrino mass decay, the neutrino mass scale and the sum of the neutrino mass in the inverted and degenerate mass spectrum. Thus, this model may be testable by future experiments that focus in neutrinoless double beta decay.
We study the experimental constraints on strongly interacting vector-fermions compatible with the relaxion mechanism and investigate any possible tuning. The focus is on a minimal model and low confinement scale. More precisely, we study bounds from electroweak precision tests, Higgs decay, Big Bang nucleosynthesis and direct collider searches. The effect of these new fermions on vacuum stability is also investigated. Combining our bounds, we show that the relaxion mechanism becomes increasingly constrained and fine-tuned as the confinement scale decreases. For example, a confinement scale of a few tens of MeVs would require tuning at the percent level.
The MATHUSLA detector is a simple large-volume tracking detector to be located on the surface above one of the general-purpose experiments at the Large Hadron Collider. This detector was proposed in [1] to detect exotic, neutral, long-lived particles that might be produced in high-energy proton-proton collisions. In this paper, we consider the use of the limited information that MATHUSLA would provide on the decay products of the long-lived particle. For the case in which the long-lived particle is pair-produced in Higgs boson decays, we show that it is possible to measure the mass of this particle and determine the dominant decay mode with less than 100 observed events. We discuss the ability of MATHUSLA to distinguish the production mode of the long-lived particle and to determine its mass and spin in more general cases.
According to the standard model, the Cabibbo-favored (CF) decays are CP conserve at tree level. Observation of any finite CP asymmetry can be received as a signal of new physics. In CF charm meson decays, D0→K−π+ and D+→Ks0π+, the following experimental values for their CP asymmetry are reported, respectively: (0.3±0.7) % and (−0.41±0.09) %. The value of the later can be attributed to the mixing of K0 and K0, however, its contribution is about (−0.332±0.006) %. In this paper, we use these experimental results to constrain the unparticle stuff as a new physics which may contribute to these CP asymmetries.
We investigate the transverse charge densities of the deuteron in a soft-wall AdS/QCD model by considering both the unpolarized and the transversely polarized cases. The deuteron form factors are derived from the soft-wall AdS/QCD model and it is shown that the calculated results agree with the phenomenological parametrization and experimental data. The transverse charge densities of the deuteron are also derived from the soft-wall AdS/QCD model, and we notice slight deviations from those of the phenomenological parametrization.
We consider pair-production of electroweakinos promptly decaying to light gravitinos in general gauge mediation scenarios within the minimal supersymmetric standard model. Typically the presence of photons and missing transverse momentum is the key signature for this kind of scenarios. We highlight where LHC analyses which have originally been designed to probe different scenarios provide complementary constraints with respect to the dedicated searches and we present the constraints on the parameter space.
We discuss the role of meson exchange mechanisms in γγ→γγ scattering. Several pseudoscalar (π0, η, η′(958), ηc(1S), ηc(2S)), scalar (f0(500), f0(980), a0(980), f0(1370), χc0(1P)) and tensor (f2(1270), a2(1320), f2′(1525), f2(1565), a2(1700)) mesons are taken into account. We consider not only s-channel but also for the first time t- and u-channel meson exchange amplitudes corrected for off-shell effects including vertex form factors. We find that, depending on not well known vertex form factors, the meson exchange amplitudes interfere among themselves and could interfere with fermion-box amplitudes and modify the resulting cross sections. The meson contributions are shown as a function of collision energy as well as angular distributions are presented. Interesting interference effects separately for light pseudoscalar, scalar and tensor meson groups are discussed. The meson exchange contributions may be potentially important in the context of a measurement performed recently in ultraperipheral collisions of heavy ions by the ATLAS collaboration. The light-by-light interactions could be studied in future in electron-positron collisions by the Belle II at SuperKEKB accelerator.
Dark matter (DM) direct detections are investigated for models with the following properties: isospin-violating couplings, exothermic scatterings, and/or a light mediator, with the aim to reduce the tension between the CDMS-Si positive signals and other negative searches. In particular, we focus on the non-standard effective operators which could lead to the spin-independent DM-nucleus scatterings with non-trivial dependences on the transfer momentum or DM velocity. As a result, such effective operator choices have the very mild effects on the final fittings. Furthermore, by including the latest constraints from LUX, PandaX-II, XENON1T and PICO-60, we find that, for almost all the considered models, the predicted CDMS-Si signal regions are either severely constrained or completely excluded by the LUX, PandaX-II, XENON1T and PICO-60 data, including the most promising Xe-phobic exothermic DM models with/without a light mediator. Therefore, we conclude that it is very difficult for the present DM framework to explain the CDMS-Si excess.
Of late, a number of instances of neutrino flux anomalies observed at short-baselines have given traction to the hypothesis of adding new neutrino flavours to our Standard Model set, albeit ones not associated with a partnered lepton. Anomalies observed at LSND, MiniBooNE and at short distances from nuclear reactors have suggested the existence of sterile mass states with masses on the scale of ∼1eV, prompting further investigations. Subsequently, Fermilab is set to host a Short-Baseline Neutrino (SBN) oscillation program which will cross-check each of these anomalies by deploying three state-of-the-art liquid argon detectors along the Booster Neutrino Beamline. Through an event-by-event Monte Carlo simulation study, this document presents short-baseline oscillation sensitivity predictions for SBN on a purely statistical basis in the scope of a 3+1 sterile neutrino model approximated with a two flavour mixing basis. As a world's first, sensitivities in parameter space to 3+1 mixing angles θ14 and θ24 are presented, in addition to the sensitivities gained by combining νμ disappearance and νe appearance channel data. Provided also are energy spectra and 3+1 oscillation parameter sensitivity predictions for these two individual channels. The results agreed with parameter space sensitivity predictions already conceived by Fermilab to a satisfactory degree.
We consider a scenario inspired by natural supersymmetry, where neutrino data is explained within a low-scale seesaw scenario. We extend the Minimal Supersymmetric Standard Model by adding light right-handed neutrinos and their superpartners, the R-sneutrinos, and consider the lightest neutralinos to be higgsino-like. We consider the possibilities of having either an R-sneutrino or a higgsino as lightest supersymmetric particle. Assuming that squarks and gauginos are heavy, we systematically evaluate the bounds on slepton masses due to existing LHC data.
Recently, Liou, Mueller and Munier have argued that proton-nucleus collisions at the LHC may give access to the full statistics of the event-by-event fluctuations of the gluon density in the proton. Indeed, the number of particles produced in an event in rapidity slices in the fragmentation region of the proton may, under some well-defined assumptions, be directly related to the number of gluons which have a transverse momentum larger than the nuclear saturation scale present in the proton at the time of the interaction with the nucleus. A first calculation of the probability distribution of the number of gluons in a hadron was performed, using the color dipole model. In this talk, we review this proposal, and present preliminary numerical calculations which support the analytical results obtained so far.
Complex parameters in the MSSM lead to mixing and interference between the two heavier neutral CP-even and CP-odd Higgs states. These effects can become very large in the case of almost degenerate states. In a CP-violating benchmark scenario, we investigate phenomenological implications of such interferences in view of the LHC searches for heavy Higgs bosons decaying to a pair of τ-leptons and produced in gluon fusion and in association with b-quarks. Strongly destructive effects leave parameter regions unconstrained that would be regarded as excluded if no interference terms were taken into account.
We present an algorithm to combine multiple matrix elements at LO and NLO with a parton shower. We build on the unitarized merging paradigm. The inclusion of higher orders and multiplicities reduce the scale uncertainties for observables sensitive to hard emissions, while preserving the features of inclusive quantities. The combination allows further soft and collinear emissions to be predicted by the all-order parton shower approximation. We inspect the impact of terms that are formally but not parametrically negligible. We present results for a number of collider observables where multiple jets are observed, either on their own or in the presence of additional uncoloured particles. The algorithm is implemented in the event generator Herwig.
We compare predictions of nCTEQ15 nuclear parton distribution functions with proton-lead vector boson production data from the LHC. We select data sets that are most sensitive to nuclear PDFs and have potential to constrain them. We identify the kinematic regions and flavours where these data can bring new information and will have largest impact on the nuclear PDFs. Finally, we estimate the effect of including these data in a global analysis using a reweighting method.
Cross section predictions of W and Z bosons in association with jets (up to 6 jets, W→ℓ±ν and Z→ℓ± where ℓ±=e± or μ±) in proton-proton collisions at s=14 TeV is performed using Alpgen MC generator with CTEQ6L1 leading order parton distribution function. In addition, W and Z boson cross sections are obtained up to next to next to leading order (NNLO) QCD corrections using MCFM MC generator. To validate the predictions, a detailed comparison of NNLO QCD calculations with 8 TeV CMS results for total cross section is performed and a fiducial region is further defined to make a comparison of predictions with 7 TeV and 13 TeV ATLAS results.
We derive new constraints on light vectors coupled to Standard Model (SM) fermions, when the corresponding SM current is broken by the chiral anomaly. Cancellation of the anomaly by heavy fermions results, in the low-energy theory, in Wess-Zumino type interactions between the new vector and the SM gauge bosons. These interactions are determined by the requirement that the heavy sector preserves the SM gauge groups, and lead to (energy / vector mass)^2 enhanced rates for processes involving the longitudinal mode of the new vector. Taking the example of a vector coupled to baryon number, Z decays and flavour changing neutral current meson decays via the new vector can occur with (weak scale / vector mass)^2 enhanced rates. These processes place significantly stronger coupling bounds than others considered in the literature, over a wide range of vector masses.
Cold, ultralight (≪ eV) bosonic dark matter with a misalignment abundance can induce temporal variation in the masses and couplings of Standard Model particles. We find that fast variations in neutrino oscillation parameters can lead to significantly distorted neutrino oscillations (DiNOs) and yield striking signatures at long baseline experiments. We study several representative observables to demonstrate this effect and find that current and future experiments including DUNE and JUNO are sensitive to a wide range of viable scalar parameters over many decades in mass reach.
We show that the assumption of non-zero topological susceptibility of the vacuum in a fermion-free version of a theory, such as gravity or QCD, suffices to conclude the following: Once N massless fermion flavors are added to the theory, they break the chiral flavor symmetry dynamically, down to a subgroup that would be anomaly-free under gauging; In both theories, the pseudo-Goldstone corresponding to axial U(1)-symmetry becomes massive; In QCD as well as in gravity the massless fermions are eliminated from the low energy spectrum of the theory. All the above conclusions are reached without making an assumption about confinement. Some key methods of our approach are: Reformulation of topological susceptibility in the language of a three-form gauge theory; Utilization of gravity in the role of a spectator interaction for the chiral anomaly-matching in QCD; Gauging chiral symmetries and matching their anomalies using the spectator Green-Schwarz type axions. Our observations suggest that breaking of chiral symmetries in QCD and in gravity can be described in unified topological language, and seemingly-disconnected phenomena, such as, the generation of eta'-meson mass in QCD and breaking of global chiral symmetry by gravity may share a secret analogy. The described phenomenon may shed a new light - via contribution of micro black holes into the gravitational topological susceptibility of the vacuum - on incompatibility between black holes and global symmetries. It appears that explicit breaking is not the sole possibility, and like QCD, gravity may break global symmetries dynamically. As an useful byproduct, matching of gravitational anomalies provides a selection tool for compositeness, eliminating possibility of massless composite fermions where standard gauge anomaly matching would allow for their existence.
It is a common problem in lattice QCD calculation of the mass of the hadron with an annihilation channel that the signal falls off in time while the noise remains constant. In addition, the disconnected insertion calculation of the three-point function and the calculation of the neutron electric dipole moment with the θ term suffer from a noise problem due to the V fluctuation. We identify these problems to have the same origin and the V problem can be overcome by utilizing the cluster decomposition principle. We demonstrate this by considering the calculations of the glueball mass, the strangeness content in the nucleon, and the CP violation angle in the nucleon due to the θ term. It is found that for lattices with physical sizes of 4.5 - 5.5 fm, the statistical errors of these quantities can be reduced by a factor of 3 to 4. The systematic errors can be estimated from the Akaike information criterion. For the strangeness content, we find that the systematic error is of the same size as that of the statistical one when the cluster decomposition principle is utilized. This results in a 2 to 3 times reduction in the overall error.
A unified field theory of all known basic forces and elementary particles is built based on the postulates of gauge invariance and coordinate independence along with general conformal scaling symmetry. The hyper-spin charge of a unified hyper-spinor field is conjectured to correlate with the dimension of hyper-spacetime. The minimal dimension of hyper-spacetime for the unity of quarks and leptons in the standard model is found to be Dh=19 with a bimaximal symmetry. A unified fundamental interaction is governed by hyper-spin gauge symmetry SP(1,Dh-1). We show gravitational origin of gauge symmetry characterized by gauge-type Goldstone-like hyper-gravifield, which enables us to study gauge gravity and gravity geometry correspondences and to reveal gauge geometry duality.
Cosmic birefringence is the process that rotates the plane of polarization by an amount, α, as photons propagate through free space. Such an effect arises in parity-violating extensions to the electromagnetic sector, such as the Chern-Simons term common in axion models, quintessence models, or Lorentz-violating extensions to the standard model. Most studies consider the monopole of this rotation, but it is also possible for the effect to have spatial anisotropies. Paying particular attention to large scales, we implement a novel pixel-based method to extract the spherical harmonics for L≤30 and a pseudo-CL method for L>30. Our results are consistent with no detection and we set 95% upper limits on the amplitude of a scale-invariant power spectrum of L(L+1)CL/2π<[2.2(stat.)±0.7(syst.)]×10−5=[0.07(stat.)±0.02(syst.)]deg2, on par with previous constraints. This implies specific limits on the dipole and quadrupole amplitudes to be C1/4π<0.2∘ and C2/4π<0.1∘, at 95% CL, respectively, improving previous constraints by an order of magnitude. We further constrain a model independent M=0 quadrupole in an arbitrary direction to be α20=0.02∘±0.21∘, with an unconstrained direction. However, we find an excess of dipolar power with an amplitude 3C1/4π=0.32∘±0.10∘(stat.)±0.08∘(syst.), in the direction (l,b)=(295∘,17∘)±(22∘,17∘)(stat.)±(5∘,16∘)(syst.), larger than 1.4% of simulations with no birefringence. We attribute part of this signal to the contamination of residual foregrounds not accounted for in our simulations, although this should be further investigated.
We analyze the peripheral structure of the nucleon-nucleon interaction for LAB energies below 350 MeV. To this end we transform the scattering matrix into the impact parameter representation by analyzing the scaled phase shifts (L+1/2)δJLS(p) and the scaled mixing parameters (L+1/2)ϵJLS(p) in terms of the impact parameter b=(L+1/2)/p. According to the eikonal approximation, at large angular momentum L these functions should become an universal function of b, {\it independent} on L. This allows to discuss in a rather transparent way the role of statistical and systematic uncertainties in the different long range components of the two-body potential. Implications for peripheral waves obtained in chiral perturbation theory interactions to fifth order (N5LO) or from the large body of NN data considered in the SAID partial wave analysis are also drawn from comparing them with other phenomenological high-quality interactions, constructed to fit scattering data as well. We find that both N5LO and SAID peripheral waves disagree more than 5σ with the Granada-2013 statistical analysis, more than 2σ with the 6 statistically equivalent potentials fitting the Granada-2013 database and about 1σ with the historical set of 13 high-quality potentials developed since the 1993 Nijmegen analysis.
ϕ-meson--nucleus bound state energies and absorption widths are calculated for seven selected nuclei by solving the Klein-Gordon equation with complex optical potentials. Essential input for the calculations, namely the medium-modified K and K meson masses, as well as the density distributions in nuclei, are obtained from the quark-meson coupling model. The attractive potential for the ϕ-meson in the nuclear medium originates from the in-medium enhanced KK loop in the ϕ-meson self-energy. The results suggest that the ϕ-meson should form bound states with all the nuclei considered. However, the identification of the signal for these predicted bound states will need careful investigation because of their sizable absorption widths.
We report the first dark matter search results from XENON1T, a ∼2000-kg-target-mass dual-phase (liquid-gas) xenon time projection chamber in operation at the Laboratori Nazionali del Gran Sasso in Italy and the first ton-scale detector of this kind. The blinded search used 34.2 live days of data acquired between November 2016 and January 2017. Inside the (1042±12) kg fiducial mass and in the [5, 40] keVnr energy range of interest for WIMP dark matter searches, the electronic recoil background was (1.93±0.25)×10−4 events/(kg × day ×keVee), the lowest ever achieved in a dark matter detector. A profile likelihood analysis shows that the data is consistent with the background-only hypothesis. We derive the most stringent exclusion limits on the spin-independent WIMP-nucleon interaction cross section for WIMP masses above 10 GeV/c2, with a minimum of 7.7 ×10−47 cm2 for 35-GeV/c2 WIMPs at 90% confidence level.
Despite the outstanding achievements of modern cosmology, the classical dispute on the precise value of H0, which is the first ever parameter of modern cosmology and one of the prime parameters in the field, still goes on and on after over half a century of measurements. Recently the dispute came to the spotlight with renewed strength owing to the significant tension (at >3σ c.l.) between the latest Planck determination obtained from the CMB anisotropies and the local (distance ladder) measurement from the Hubble Space Telescope (HST), based on Cepheids. In this work, we investigate the impact of the running vacuum model (RVM) and related models on such a controversy. For the RVM, the vacuum energy density ρΛ carries a mild dependence on the cosmic expansion rate, i.e. ρΛ(H), which allows to ameliorate the fit quality to the overall SNIa+BAO+H(z)+LSS+CMB cosmological observations as compared to the concordance ΛCDM model. By letting the RVM to deviate from the vacuum option, the equation of state w=−1 continues to be favored by the overall fit. Vacuum dynamics also predicts the following: i) the CMB range of values for H0 is more favored than the local ones, and ii) smaller values for σ8(0). As a result, a better account for the LSS structure formation data is achieved as compared to the ΛCDM, which is based on a rigid (i.e. non-dynamical) Λ term.
* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.