HEP Phenomenology·hep-ph
16 papers—10 primary·6 cross-listed·reconstructed*
Neutrino experiments can be considered sensitive tools to test Lorentz and CPT invariance. Taking advantage of the great variety of neutrino experiments, including neutrino oscillations, weak decays, and astrophysical neutrinos, the generic experimental signatures of the breakdown of these fundamental symmetries in the neutrino sector are presented.
David Emmanuel-Costa🇵🇹 · Ricardo Gonzalez Felipe🇵🇹
We look for all weak bases that lead to texture zeroes in the quark mass matrices and contain a minimal number of parameters in the framework of the standard model. Since there are ten physical observables, namely, six nonvanishing quark masses, three mixing angles and one CP phase, the maximum number of texture zeroes in both quark sectors is altogether nine. The nine zero entries can only be distributed between the up- and down-quark sectors in matrix pairs with six and three texture zeroes or five and four texture zeroes. In the weak basis where a quark mass matrix is nonsingular and has six zeroes in one sector, we find that there are 54 matrices with three zeroes in the other sector, obtainable through right-handed weak basis transformations. It is also found that all pairs composed of a nonsingular matrix with five zeroes and a nonsingular and nondecoupled matrix with four zeroes simply correspond to a weak basis choice. Without any further assumptions, none of these pairs of up- and down-quark mass matrices has physical content. It is shown that all non-weak-basis pairs of quark mass matrices that contain nine zeroes are not compatible with current experimental data. The particular case of the so-called nearest-neighbour-interaction pattern is also discussed.
Lorenzo Bartolini🇮🇹 · Francesco Bigazzi🇮🇹 · Stefano Bolognesi🇮🇹 · Aldo L. Cotrone🇮🇹 · Andrea Manenti🇨🇭
We compute the electric dipole moment of nucleons in the large QCD model by Witten, Sakai and Sugimoto with degenerate massive flavors. Baryons in the model are instantonic solitons of an effective five-dimensional action describing the whole tower of mesonic fields. We find that the dipole electromagnetic form factor of the nucleons, induced by a finite topological angle, exhibits complete vector meson dominance. We are able to evaluate the contribution of each vector meson to the final result - a small number of modes are relevant to obtain an accurate estimate. Extrapolating the model parameters to real QCD data, the neutron electric dipole moment is evaluated to be . The electric dipole moment of the proton is exactly the opposite.
M. Sruthilaya🇮🇳 · Srinu Gollu🇮🇳
To accommodate the recently observed non-zero reactor mixing angle , we consider the lepton mixing matrix as Tri-bimaximal mixing (TBM) form in the leading order along with a perturbation in neutrino sector. The perturbation is taken to be a rotation in 23 plane followed by a rotation in 13 plane, i.e., . We obtain the allowed values of the parameters , and , which can accommodate all the observed mixing angles consistently and calculate the phenomenological observables such as the Dirac CP violating phase (), Jarlskog invariant (), effective majorana mass , and , the electron neutrino mass. We find that can take any values between and and always comes below its experimental upper limit.
We present an alternative interpretation within the Standard Model of the new LHC resonance at . We further elaborate on our previous proposal that the resonance at 125 GeV could be interpreted as a pseudoscalar meson with quantum number . We develop a phenomenological approach where this pseudoscalar mimics the decays of the Standard Model Higgs boson in the vector boson decay channels. We propose that the true Higgs boson should be a heavy resonance with mass of as argued in Ref.~\cite{Cea:2012}. We determine the most relevant decay modes and estimate the partial decay widths and branching ratios. We also discuss briefly the experimental signatures of this heavy Higgs boson. Finally, we attempt a comparison of our theoretical expectations with recent data at from ATLAS and CMS experiments in the so-called golden channel. We find that the available experimental data could be consistent with the heavy Higgs scenario.
K. Azizi🇹🇷 · A. T. Olgun🇹🇷 · Z. Tavukoglu🇹🇷
We present a study on the impact of scalar leptoquarks on the semileptonic decays of , and . To this end, we calculate the differential branching ratio and lepton forward-backward asymmetry defining the processes , and , with being or , using the form factors calculated via light cone QCD in full theory. In calculations, the errors of form factors are taken into account. We compare the results obtained in leptoquark model with those of the standard model as well as the existing lattice QCD predictions and experimental data.
Simone Alioli🇨🇭 · Fabrizio Caola🇨🇭 · Gionata Luisoni🇨🇭 · Raul Röntsch🇩🇪
We present a calculation of the next-to-leading order (NLO) QCD corrections to the hadroproduction process , matched to the parton shower in the POWHEG framework. We take advantage of the POWHEG BOX tool for the implementation and rely on PYTHIA 8 for the showering and hadronization stages. We fully include interference effects, while also covering the single-resonant region. For this phenomenological study we focus on four lepton production as a signal process, neglecting all quark mass effects as well as the Higgs-mediated contributions, which are known to be subdominant in this case. We provide predictions from our simulations for the 13 TeV LHC Run II setup, including realistic experimental cuts.
S.P. Jones🇩🇪 · A.D. Martin🇬🇧 · M.G. Ryskin🇬🇧 · T. Teubner🇬🇧
We address the question as to whether data for J/\psi mesons produced exclusively in the forward direction at the LHC can be used in global parton analyses (based on collinear factorization) to pin down the low x gluon PDF. We show that it may be possible to overcome the problems that (i) the process is described by a skewed or Generalized Parton Distribution (GPD), (ii) it is very sensitive to the choice of factorization scale and (iii) there is bad LO, NLO,... perturbative stability to the predictions. However, we start by briefly explaining how the alternative k_T factorization approach has been used to describe the process.
Florez Andres🇨🇴 · Gurrola Alfredo🇺🇸 · Johns Will🇺🇸 · Do oh Young🇰🇷 · Sheldon Paul🇺🇸 · Teague Dylan🇺🇸 · Weiler Thomas🇺🇸
New massive resonances are predicted in many extensions to the Standard Model (SM) of particle physics and constitutes one of the most promising searches for new physics at the LHC. We present a feasibility study to search for new heavy neutral gauge bosons using vector boson fusion (VBF) processes, which become especially important as the LHC probes higher collision energies. In particular, we consider the possibility that the discovery of a boson may have eluded searches at the LHC. The coupling of the boson to the SM quarks can be small, and thus the would not be discoverable by the searches conducted thus far. In the context of a simplified phenomenological approach, we consider the and decay modes to show that the requirement of a dilepton pair combined with two high forward jets with large separation in pseudorapidity and with large dijet mass is effective in reducing SM backgrounds. The expected exclusion bounds (at 95\% confidence level) are TeV and TeV in the and channels, respectively, assuming 1000 fb of 13 TeV data from the LHC. The use of the VBF topology to search for massive neutral gauge bosons provides a discovery reach with expected significances greater than 5 (3) for masses up to 1.4 (1.6) TeV and 2.0 (2.2) TeV in the and channels.
I discuss the two-particle subleading power corrections in radiative leptonic decay at next-to-leading order in with the dispersion approach. Employing the method of regions, factorization of the form factors is demonstrated explicitly, at one loop, for a space-like hard-collinear photon. The two-particle soft (end-point) contribution is shown to be suppressed by one power of , in the heavy quark limit, compared with the leading power contribution computed from QCD factorization. I further report the recent calculation on the three-particle subleading power contribution to the on-shell form factors at tree level and demonstrate that the "soft" and the "hard" three-particle corrections are of the same power, in contrast to the two-particle counterparts, as already speculated from the rapidity divergence in the corresponding factorization formulae. Phenomenological implications of the subleading power contributions to the amplitude are also addressed in detail, focusing on the determination of the inverse moment of the leading-twist -meson distribution amplitude.
Kurt Hinterbichler🇺🇸 · Austin Joyce🇺🇸 · Justin Khoury🇺🇸
We investigate the symmetry structure of inflation in 2+1 dimensions. In particular, we show that the asymptotic symmetries of three-dimensional de Sitter space are in one-to-one correspondence with cosmological adiabatic modes for the curvature perturbation. In 2+1 dimensions, the asymptotic symmetry algebra is infinite-dimensional, given by two copies of the Virasoro algebra, and can be traced to the conformal symmetries of the two-dimensional spatial slices of de Sitter. We study the consequences of this infinite-dimensional symmetry for inflationary correlation functions, finding new soft theorems that hold only in 2+1 dimensions. Expanding the correlation functions as a power series in the soft momentum , these relations constrain the traceless part of the tensorial coefficient at each order in in terms of a lower-point function. As a check, we verify that the identity is satisfied by inflationary correlation functions in the limit of small sound speed.
Recent experiments on lead (\textrm{}) nuclei have observed the celebrated phenomenon of neutron skin-thickness of low energy nuclear physics. The skin-thickness provides a measure of extension of spatial distribution of neutrons inside the atomic nucleus than protons. We have studied the effect of neutron skin-thickness on inclusive prompt photon production in Pb~+~Pb collisions at the Large Hadron Collider energies. We have calculated the \textquoteleft central-to-peripheral ratio\textquoteright () of prompt photon production with and without accounting for neutron skin effect. The neutron skin causes a characteristic enhancement in the ratio, in particular at forward rapidity, which is distinguishable in our calculation. However a very precise direct photon measurement up to large transverse momenta would be necessary to constrain the feature in experiment.
Fast radio bursts can be caused by some phenomena related to 'new physics'.One of the most prominent candidates of the kind are axion Bose stars which can engender bursts when undergoing conversion into photons in magnetospheres of neutron stars or during their collapse. In this short research note an importance of three observational criteria is outlined, namely total energetic, (ms) duration and non-monochromatic shape of the spectrum. It is shown that it is impossible to meet these criteria in simplified models of axion-neutron star interaction scenario and thorough investigation of more complex models which involve back-reaction and non-linear effects are needed in order to explain FRBs within this scenario.
We consider the electromagnetic production of positron in collision of slow heavy nuclei, with the simultaneously produced electron captured by one of the nuclei. The cross-section of the discussed process exceeds essentially the cross-section of production.
Jussi Auvinen🇺🇸 · Krzysztof Redlich🇵🇱 · Steffen A. Bass🇺🇸
We systematically compare an event-by-event transport+viscous hydrodynamics hybrid model to data from the RHIC beam energy scan using a general Bayesian method. We demonstrate how the inclusion of multistrange hadron observables affects the outcome of the Bayesian analysis and conduct an in depth analysis of the viability of and as probes of the transition region between a deconfined quark-gluon plasma and hadronic phase in heavy ion collisions at higher-end RHIC collision energies. Utilizing UrQMD to model the final hadronic interactions, we examine the collision rates of and and the modification to their transverse momentum spectra due to these interactions.
Jussi Auvinen🇺🇸 · Jonah E. Bernhard🇺🇸 · Steffen A. Bass🇺🇸
We investigate the collision energy dependence of shear viscosity over the entropy density ratio in Au+Au collisions at , and GeV, using Bayesian statistical analysis and Gaussian process emulators to explore the full input parameter space of a transport+hydrodynamics hybrid model. The ratio is found to decrease as a function of collision energy, supporting the results from previous studies performed with the same hybrid model.
* 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.