Thu·Oct 5, 2017Thursday·October 5, 2017

1. 01*

   Lepton mass effects and angular observables in ${\Lambda }_b\to \Lambda (\to p\pi ){\ell }^{+}{\ell }^{-}$

   Shibasis Roy🇮🇳 · Ria Sain🇮🇳 · Rahul Sinha🇮🇳

   The flavor changing rare decay $B\to K^{\ast }(\to K\pi ){\ell }^{+}{\ell }^{-}$ is one of the most studied modes due to its sensitivity to physics beyond the standard model and several discrepancies have come to light among the plethora of observables that are measured. In this paper we revisit the analogous baryonic decay mode ${\Lambda }_b\to \Lambda (\to p\pi ){\ell }^{+}{\ell }^{-}$ and we present a complete set of ten angular observables that can be measured using this decay mode. Our calculations are done retaining the finite lepton mass so that the signal of lepton non-universality observed in $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$ can be corroborated by the corresponding baryonic decay mode. We show that due to the parity violating nature of the subsequent $\Lambda \to p\pi$ decay there exist at least one angular asymmetry that is non-vanishing in the large recoil limit unlike the case in $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$ decay mode, making it particularly sensitive to new physics that violates lepton flavor universality.

   hep-phPRD(2017)·28 citations
2. 02*

   Exponential Hierarchies from Anderson Localization in Theory Space

   Nathaniel Craig🇺🇸 · Dave Sutherland🇺🇸

   We present a new mechanism for generating exponential hierarchies in four-dimensional field theories inspired by Anderson localization in one dimension, exploiting an analogy between the localization of electron energy eigenstates along a one-dimensional disordered wire and the localization of mass eigenstates along a local "theory space" with random mass parameters. Mass eigenstates are localized even at arbitrarily weak disorder, with exponentially suppressed couplings to sites in the theory space. The mechanism is quite general and may be used to exponentially localize fields of any spin. We apply the localization mechanism to two hierarchies in Standard Model parameters --- the smallness of neutrino masses and the ordering of quark masses --- and comment on possible relevance to the electroweak hierarchy problem. This raises the compelling possibility that some of the large hierarchies observed in and beyond the Standard Model may result from disorder, rather than order.

   hep-phPRL(2018)·28 citations
3. 03*

   Minimal $SU(3)\times SU(3)$ symmetry breaking patterns

   Yang Bai🇺🇸 · Bogdan A. Dobrescu🇺🇸

   We study the vacua of an $SU(3)\times SU(3)$-symmetric model with a bifundamental scalar. Structures of this type appear in various gauge theories such as the Renormalizable Coloron Model, which is an extension of QCD, or the Trinification extension of the electroweak group. In other contexts, such as chiral symmetry, $SU(3)\times SU(3)$ is a global symmetry. As opposed to more general $SU(N)\times SU(N)$ symmetric models, the $N=3$ case is special due to the presence of a trilinear scalar term in the potential. We find that the most general tree-level potential has only three types of minima: one that preserves the diagonal $SU(3)$ subgroup, one that is $SU(2)\times SU(2)\times U(1)$ symmetric, and a trivial one where the full symmetry remains unbroken. The phase diagram is complicated, with some regions where there is a unique minimum, and other regions where two minima coexist.

   hep-phPRD(2018)·27 citations
4. 04*

   Pitfalls of iterative pole mass calculation in electroweak multiplets

   James McKay🇬🇧 · Pat Scott🇬🇧 · Peter Athron🇦🇺

   The radiatively-induced mass splitting between components of an electroweak multiplet is typically of order 100 MeV. This is sufficient to endow the charged components with macroscopically-observable lifetimes, and ensure an electrically-neutral dark matter particle. We show that a commonly used iterative procedure to compute radiatively-corrected pole masses can lead to very different mass splittings than a non-iterative calculation at the same loop order. By estimating the uncertainties of the two one-loop results, we show that the iterative procedure is significantly more sensitive to the choice of renormalisation scale and gauge parameter than the non-iterative method. This can cause the lifetime of the charged component to vary by up to 12 orders of magnitude if iteration is employed. We show that individual pole masses exhibit similar scale-dependence regardless of the procedure, but that the leading scale-dependent terms cancel when computing the mass splitting if and only if the non-iterative procedure is employed. We show that this behaviour persists at two-loop order: the precision of the mass splitting improves in the non-iterative approach, but our results suggest that higher-order corrections do not reduce the uncertainty in the iterative calculation enough to resolve the problem at two-loop order. We conclude that the iterative procedure should not be used for computing pole masses in situations where electroweak mass splittings are phenomenologically relevant.

   hep-phEur.Phys.J.Plus(2018)·11 citations
5. 05*

   Vector-like quarks and heavy coloured bosons at the LHC

   A.Deandrea🇫🇷 · A.M. Iyer🇮🇹

   We investigate the production of heavy coloured scalars and vectors and their relevance at LHC for the study of vector-like quarks ($T$). These coloured states ($C$) are present in a large number of extensions of the standard model, in particular in composite models and in extra dimensional models. Assuming that these bosonic states are heavier than the vector-like quarks (VLQ), we consider their production through the process $pp\to C\to tT$. Large QCD production cross-sections for $C$ enable us to probe heavier masses for the VLQ and thereby allowing to put stronger limits on the vector-like quarks which are produced in their decay chain. We adopt a universal analysis strategy by including leptons under the classification of `jets', thereby limiting the bias towards a specific combination of final state. We also study the possibility of disentangling these scenarios from supersymmetric extensions of the Standard Model by using simple discriminants based on jet multiplicity and missing energy. We demonstrate that a simple set of cuts are sufficient to disentangle the VLQ signal from the backgrounds. In models with a moderate $B.R.(C\to Tt)$, the analysis enables one to get a hint of VLQ masses as heavy as 3 TeV.

   hep-phhep-exPRD(2018)·14 citations
6. 06*

   Right-handed Neutrino Dark Matter in a U(1) Extension of the Standard Model

   Peter Cox🇯🇵 · Chengcheng Han🇯🇵 · Tsutomu T. Yanagida🇯🇵

   We consider minimal $U(1)$ extensions of the Standard Model in which one of the right-handed neutrinos is charged under the new gauge symmetry and plays the role of dark matter. In particular, we perform a detailed phenomenological study for the case of a $U(1{)}_{(B-L{)}_3}$ flavoured $B-L$ symmetry. If perturbativity is required up to high-scales, we find an upper bound on the dark matter mass of $m_{\chi }\lesssim 2$ TeV, significantly stronger than that obtained in simplified models. Furthermore, if the $U(1{)}_{(B-L{)}_3}$ breaking scalar has significant mixing with the SM Higgs, there are already strong constraints from direct detection. On the other hand, there remains significant viable parameter space in the case of small mixing, which may be probed in the future via LHC $Z^{\prime }$ searches and indirect detection. We also comment on more general anomaly-free symmetries consistent with a TeV-scale RH neutrino dark matter candidate, and show that if two heavy RH neutrinos for leptogenesis are also required, one is naturally led to a single-parameter class of $U(1)$ symmetries.

   hep-phJCAP(2018)·23 citations
7. 07*

   Investigating the Transverse Single Spin Asymmetry in the Inelastic $J/\Psi$ photoproduction in $p^{\uparrow }p$ and $p^{\uparrow }A$ collisions

   V. P. Goncalves🇧🇷

   In this paper we propose to investigate the transverse single spin asymmetry in the inelastic $J/\Psi$ photoproduction in $p^{\uparrow }p$ and $p^{\uparrow }A$ collisions at RHIC energies. At leading order this process probes the gluon Sivers function. We predict large values for the cross sections, which indicates that its experimental analysis is, in principle, feasible. The rapidity dependence of the single spin asymmetry is presented. We obtain that the asymmetry is strongly dependent on the model used for the gluon Sivers function and that it can be probed by the analysis of the $J/\Psi$ production at forward rapidities. Our results indicate that a future experimental analysis of this process can be useful to constrain the gluon Sivers function.

   hep-phhep-exnucl-exnucl-thPRD(2018)·7 citations
8. 08*

   Measuring Polarized Gluon Distributions by Heavy Quark Spin Correlations and Polarizations

   Gary R. Goldstein🇺🇸 · S. Liuti🇺🇸

   The production of heavy flavor quark pairs, including top-anti-top, at the LHC proceeds primarily through gluon fusion. The correlation between the gluon spins affects various spin correlations between the produced quark and anti-quark. Both single spin asymmetries and double correlations of the quark pair spins will be manifest in the subsequent hadronization and decay distributions. For top pairs this is most pronounced. Dilepton, single lepton, and purely hadronic top pair decay channels allow for the extraction of gluon spin information as well as providing a window into possible interactions Beyond the Standard Model. Spin related asymmetries and polarizations will be presented. The implications for experimental determination will be discussed.

   hep-ph0 citations
9. 09*

   Pinning down the linearly-polarised gluons inside unpolarised protons using quarkonium-pair production at the LHC

   Jean-Philippe Lansberg🇫🇷 · Cristian Pisano🇮🇹 · Florent Scarpa🇫🇷 · Marc Schlegel🇩🇪

   We show that the production of J/psi or Upsilon pairs in unpolarised pp collisions is currently the best process to measure the momentum-distribution of linearly-polarised gluons inside unpolarised protons through the study of azimuthal asymmetries. Not only the short-distance coefficients for such reactions induce the largest possible cos 4 phi modulations, but analysed data are already available. Among the various final states previously studied in unpolarised pp collisions within the TMD factorisation approach, di-J/psi production exhibits by far the largest asymmetries, up to 50% in the region studied by the ATLAS and CMS experiments. In addition, we use the very recent LHCb data at 13 TeV to perform the first fit of the unpolarised transverse-momentum-dependent gluon distribution.

   hep-phhep-exnucl-exnucl-thPLB(2018)·98 citations
10. 10*

    Neutrinoless double beta decay in effective field theory: the light Majorana neutrino exchange mechanism

    V. Cirigliano🇺🇸 · W. Dekens🇺🇸 · E. Mereghetti🇺🇸 · A. Walker-Loud🇺🇸

    We present the first chiral effective theory derivation of the neutrinoless double beta-decay $nn\to pp$ potential induced by light Majorana neutrino exchange. The effective-field-theory framework has allowed us to identify and parameterize short- and long-range contributions previously missed in the literature. These contributions can not be absorbed into parameterizations of the single nucleon form factors. Starting from the quark and gluon level, we perform the matching onto chiral effective field theory and subsequently onto the nuclear potential. To derive the nuclear potential mediating neutrinoless double beta-decay, the hard, soft and potential neutrino modes must be integrated out. This is performed through next-to-next-to-leading order in the chiral power counting, in both the Weinberg and pionless schemes. At next-to-next-to-leading order, the amplitude receives additional contributions from the exchange of ultrasoft neutrinos, which can be expressed in terms of nuclear matrix elements of the weak current and excitation energies of the intermediate nucleus. These quantities also control the two-neutrino double beta-decay amplitude. Finally, we outline strategies to determine the low-energy constants that appear in the potentials, by relating them to electromagnetic couplings and/or by matching to lattice QCD calculations.

    hep-phhep-latnucl-thPRC(2018)·106 citations
11. 11*

    Rapidity profiles from 3+1D Glasma simulations with finite longitudinal thickness

    Andreas Ipp🇦🇹 · David Müller🇦🇹

    We present our progress on simulating the Glasma in the early stages of heavy ion collisions in a non-boost-invariant setting. Our approach allows us to describe colliding nuclei with finite longitudinal width by extending the McLerran-Venugopalan model to include a parameter for the Lorentz-contracted but finite extent of the nucleus in the beam direction. We determine the rapidity profile of the Glasma energy density, which shows strong deviations from the boost invariant result. Both broad and narrow profiles can be produced by varying the initial conditions. We find reasonable agreement when we compare the results to rapidity profiles of measured pion multiplicities from RHIC.

    hep-phnucl-thPoS(2017)·3 citations
12. 12*

    A Unified Model of Quarks and Leptons with a Universal Texture Zero

    Ivo de Medeiros Varzielas🇵🇹 · Graham G. Ross🇬🇧 · Jim Talbert🇩🇪

    We show that a universal texture zero in the (1,1) position of all fermionic mass matrices, including heavy right-handed Majorana neutrinos driving a type-I see-saw mechanism, can lead to a viable spectrum of mass, mixing and CP violation for both quarks and leptons, including (but not limited to) three important postdictions: the Cabibbo angle, the charged lepton masses, and the leptonic `reactor' angle. We model this texture zero with a non-Abelian discrete family symmetry that can easily be embedded in a grand unified framework, and discuss the details of the phenomenology after electroweak and family symmetry breaking. We provide an explicit numerical fit to the available data and obtain excellent agreement with the 18 observables in the charged fermion and neutrino sectors with just 9 free parameters. We further show that the vacua of our new scalar familon fields are readily aligned along desired directions in family space, and also demonstrate discrete gauge anomaly freedom at the relevant scale of our effective theory.

    hep-phJHEP(2018)·47 citations
13. 13*

    New LHC bound on low-mass diphoton resonances

    Alberto Mariotti🇧🇪 · Diego Redigolo🇮🇱 · Filippo Sala🇩🇪 · Kohsaku Tobioka🇮🇱

    We derive a new bound on diphoton resonances using inclusive diphoton cross section measurements at the LHC, in the so-far poorly constrained mass range between the Upsilon and the SM Higgs. This bound sets the current best limit on axion-like particles that couple to gluons and photons, for masses between 10 and 65 GeV. We also estimate indicative sensitivities of a dedicated diphoton LHC search in the same mass region, at 7, 8 and 14 TeV. As a byproduct of our analysis, we comment on the axion-like particle interpretation of the CMS excesses in low-mass dijet and diphoton searches.

    hep-phhep-exPLB(2018)·154 citations
14. 14*

    Subjecting dark matter candidates to the cluster test

    Theodorus Maria Nieuwenhuizen🇳🇱

    Galaxy clusters, employed by Zwicky to demonstrate the existence of dark matter, pose new stringent tests. If merging clusters demonstrate that dark matter is self-interacting with cross section $\sigma /m\sim 2$ cm${}^2$/gr, MACHOs, primordial black holes and light axions that build MACHOs are ruled out as cluster dark matter. Recent strong lensing and X-ray gas data of the quite relaxed and quite spherical cluster A1835 allow to test the cases of dark matter with Maxwell-Boltzmann, Bose-Einstein and Fermi-Dirac distribution, next to Navarro-Frenck-White profiles. Fits to all these profiles are formally rejected at over $5\sigma$, except in the fermionic situation. The interpretation in terms of (nearly) Dirac neutrinos with mass of $1.61_{-0.30}^{+0.19}$ eV/$c^2$ is consistent with results on the cluster A1689, with the WMAP, Planck and DES dark matter fractions and with the nondetection of neutrinoless double $\beta$-decay. The case will be tested in the 2018 KATRIN experiment.

    ↳ astro-ph.COhep-phFluct.Noise Lett.(2020)·4 citations
15. 15*

    Pion decay in magnetic fields

    Gunnar S. Bali🇩🇪 · Bastian B. Brandt🇩🇪 · Gergely Endrodi🇩🇪 · Benjamin Glaessle

    The leptonic decay of the charged pion in the presence of background magnetic fields is investigated using quenched Wilson fermions. It is demonstrated that the magnetic field opens up a new channel for this decay. The magnetic field-dependence of the decay constants for both the ordinary and the new channel is determined. Using these inputs from QCD, we calculate the total decay rate perturbatively.

    ↳ hep-lathep-phnucl-thEPJ Web Conf.(2018)·6 citations
16. 16*

    Brout-Englert-Higgs mechanism for accelerating observers

    Antonio Dobado🇪🇸

    In this work we consider the spontaneous symmetry breaking of the electroweak $SU(2{)}_L\times U(1{)}_Y$ gauge group into $U(1{)}_{em}$ taken place in the Standard Model of particle physics as seen from the point of view of an accelerating observer. According to the Unruh effect that observer detects the Minkowski vacuum as a thermal bath at a temperature proportional to the proper acceleration $a$. Then we show that (in a certain large $N$ limit) when the acceleration is bigger than the critical value $a_c=4\pi v$ (where $v$ is the Higgs vacuum expectation value), the electroweak $SU(2{)}_L\times U(1{)}_Y$ gauge symmetry is restored and all elementary particles become massless. In addition, even observers with $a<a_c$, can see this symmetry restoration in the region close to the Rindler horizon.

    ↳ gr-qchep-phhep-thPRD(2017)·9 citations
17. 17*

    A Bayesian analysis of inflationary primordial spectrum models using Planck data

    Simony Santos da Costa🇧🇷 · Micol Benetti🇧🇷 · Jailson Alcaniz🇧🇷

    The current available CMB data show an anomalously low value of the CMB temperature fluctuations at large angular scales (l < 40). This lack of power is not explained by the minimal LCDM model, and one of the possible mechanisms explored in the literature to address this problem is the presence of features in the primordial power spectrum (PPS) motivated by the early universe physics. In this paper, we analyse a set of cutoff inflationary PPS models using a Bayesian model comparison approach in light of the latest Cosmic Microwave Background (CMB) data from the Planck Collaboration. Our results show that the standard power-law parameterisation is preferred over all models considered in the analysis, which motivates the search for alternative explanations for the observed lack of power in the CMB anisotropy spectrum.

    ↳ astro-ph.COgr-qchep-phJCAP(2018)·28 citations
18. 18*

    Beyond CMB cosmic variance limits on reionization with the polarized SZ effect

    Joel Meyers🇨🇦 · P. Daniel Meerburg🇬🇧 · Alexander van Engelen🇨🇦 · Nicholas Battaglia🇺🇸

    Upcoming cosmic microwave background (CMB) surveys will soon make the first detection of the polarized Sunyaev-Zel'dovich effect, the linear polarization generated by the scattering of CMB photons on the free electrons present in collapsed objects. Measurement of this polarization along with knowledge of the electron density of the objects allows a determination of the quadrupolar temperature anisotropy of the CMB as viewed from the space-time location of the objects. Maps of these remote temperature quadrupoles have several cosmological applications. Here we propose a new application: reconstruction of the cosmological reionization history. We show that with quadrupole measurements out to redshift 3, constraints on the mean optical depth can be improved by an order of magnitude beyond the CMB cosmic variance limit.

    ↳ astro-ph.COastro-ph.GAhep-phPRD(2018)·29 citations
19. 19*

    Landscaping the Strong CP Problem

    Nemanja Kaloper🇺🇸 · John Terning🇺🇸

    One often hears that the strong $CP$ problem is the one problem which cannot be solved by anthropic reasoning. We argue that this is not so. Due to nonperturbative dynamics, states with a different $CP$ violating paramenter $\theta$ acquire different vacuum energies after the QCD phase transition. These add to the total variation of the cosmological constant in the putative landscape of Universes. An interesting possibility arises when the cosmological constant is mostly cancelled by the membrane nucleation mechanism. If the step size in the resulting discretuum of cosmological constants, $\Delta \Lambda$, is in the interval $(\mathrm{meV}{)}^4<\Delta \Lambda <(100\mathrm{MeV}{)}^4$, the cancellation of vacuum energy can be assisted by the scanning of $\theta$. For $(\mathrm{meV}{)}^4<\Delta \Lambda <(\mathrm{keV}{)}^4$ this yields $\theta <10^{-10}$, meeting the observational limits. This scenario opens up 24 orders of magnitude of acceptable parameter space for $\Delta \Lambda$ compared to membrane nucleation acting alone. In such a Universe one may not need a light axion to solve the strong $CP$ problem.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2019)·27 citations
20. 20*

    Could Bert, Ernie and Big Bird be 13 billion years old?

    Guido Barbiellini🇮🇹

    Possible interpretation of highest energy neutrino never detected by IceCube as cosmological neutrinos boosted by the first accelerated protons in the Universe: the Inverse Fermi scattering $p\nu \to p^{\prime }{\nu }^{\prime }$.

    ↳ astro-ph.HEhep-ph0 citations

* 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.