Fri·Mar 17, 2017Friday·March 17, 2017

1. 01*

   The anomalous U(1) global symmetry and flavors from an SU(5) x SU(5)${}^{\prime }$ GUT in $Z_{12-I}$ orbifold compactification

   Jihn E. Kim🇰🇷 · Bumseok Kyae🇰🇷 · Soonkeon Nam🇰🇷

   In string compactifications, frequently there appears the anomalous U(1) gauge symmetry which belonged to E8$\times$E8 of the heterotic string. This anomalous U(1) gauge boson obtains mass at the compactification scale, just below $10^{18}$GeV, by absorbing one pseudoscalar (corresponding to the model-independent axion) from the second rank anti-symmetric tensor field $B_{MN}$. Below the compactification scale, there results a global symmetry U(1)${}_{\mathrm{anom}}$ whose charge $Q_{\mathrm{anom}}$ is the original gauge U(1) charge. This is the most natural global symmetry, realizing the "invisible" axion. This global symmetry U(1)${}_{\mathrm{anom}}$ is suitable for a flavor symmetry. In the simplest compactification model with the flipped SU(5) grand unification, we calculate all the low energy parameters in terms of the vacuum expectation values of the standard model singlets.

   hep-phhep-thEPJC(2017)·20 citations
2. 02*

   Self-consistent radiative corrections to false vacuum decay

   Bjorn Garbrecht🇩🇪 · Peter Millington🇬🇧

   With the Higgs mass now measured at the sub-percent level, the potential metastability of the electroweak vacuum of the Standard Model (SM) motivates renewed study of false vacuum decay in quantum field theory. In this note, we describe an approach to calculating quantum corrections to the decay rate of false vacua that is able to account fully and self-consistently for the underlying inhomogeneity of the solitonic tunneling configuration. We show that this method can be applied both to theories in which the instability arises already at the level of the classical potential and those in which the instability arises entirely through radiative effects, as is the case for the SM Higgs vacuum. We analyse two simple models in the thin-wall regime, and we show that the modifications of the one-loop corrections from accounting fully for the inhomogeneity can compete at the same level as the two-loop homogeneous corrections.

   hep-phhep-thJ.Phys.Conf.Ser.(2017)·12 citations
3. 03*

   Gauge dependence in the anomalous dimension of the gauge invariant canonical decomposition for proton momentum

   Yoshio Kitadono (Lanzhou, Inst. Modern Phys.)🇨🇳 · Pengming Zhang (Lanzhou, Inst. Modern Phys.)🇨🇳

   The gauge dependence in the anomalous dimension of the gauge-invariant-canonical-energy-momentum tensor for proton is studied by the background field method. The naive calculation shows the problem, the absence of the counter term in the gluonic sectors. The analysis shows that the result [Chen et al., Phys. Rev. Lett. 103, 062001 (2009)] is derived from the background field method after we introduced a trick to avoid the problem except for the gluon-to-gluon sector; it is gauge dependent. The possible reason of this gauge-dependent result comes from the nontrivial treatment of the condition $F_{pure}^{\mu \nu }=0$ at a higher order. This result shows that one needs a further improvement in treating this condition with a covariant way at a higher order by the background field method. In particular, we have to focus on two checkpoints, the gauge independence and zero eigenvalue in the anomalous-dimension matrix, in order to test the validity of the gauge-invariant-canonical-energy-momentum tensor.

   hep-ph0 citations
4. 04*

   Flavon-induced lepton flavour violation

   Venus Keus🇫🇮

   ATLAS and CMS have observed a flavor violating decay of the Higgs to muon and tau. The fact that flavour violating couplings of the Higgs boson are exactly zero in the Standard Model suggests the mixing of the Higgs with another scalar with flavour violating couplings. We use the flavon field from the Froggatt-Nielsen mechanism, responsible for generating the lepton Yukawa matrices, for this purpose. The parameter space is constrained from experimental bounds on charged lepton flavor violation in other processes, however, we show that a substantial region of parameter space survives these bounds while producing a large enough $Br(h\to \mu \tau )$.

   hep-phJ.Phys.Conf.Ser.(2017)·1 citation
5. 05*

   Constraining new resonant physics with top spin polarisation information

   Christoph Englert🇬🇧 · James Ferrando🇩🇪 · Karl Nordström🇬🇧

   We provide a comprehensive analysis of the power of including top quark-polarisation information to kinematically challenging $t\bar{t}$ resonance searches, for which ATLAS and CMS start losing sensitivity. Following the general modeling and analysis strategies pursued by the experiments, we analyse the semi-leptonic and the di-lepton $t\bar{t}$ channels and show that including polarisation information can lead to large improvements in the limit setting procedures with large data sets. This will allow us to set limits for parameter choices where sensitivity from $m(t\bar{t})$ is not sufficient. This highlights the importance of spin observables as part of a more comprehensive set of observables to gain sensitivity to BSM resonance searches.

   hep-phhep-exEPJC(2017)·2 citations
6. 06*

   Behavior Of Very High Energy Hadronic Cross Sections

   Leo Stodolsky🇩🇪

   The understanding of very energy hadron cross sections in terms of a 'black disc' with an 'edge' is reviewed. The slow approach to 'Asymptopia' is explained by the 'Edge'. The disproportion of length or mass scales involved is probably due to the small pion massa.

   hep-phMod.Phys.Lett.A(2017)·7 citations
7. 07*

   Jet clustering dependence of VBF Higgs production

   Michael Rauch🇩🇪 · Dieter Zeppenfeld🇩🇪

   Precise predictions for Higgs production via vector-boson fusion play an important role when testing the properties of the Higgs boson and probing new-physics effects. While the inclusive cross section changes little when including NNLO and N3LO QCD corrections, a differential NNLO calculation with typical VBF cuts shows large corrections of up to 10% in distributions. In this article, we investigate the dependence of the differential NNLO QCD calculation on the jet definition. Starting from the known results at a fixed jet clustering choice, we use the electroweak H+3 jets production cross section at NLO precision to derive NNLO results for H+2 jets production for other jet definitions. We find that larger clustering radii significantly reduce the impact of NNLO corrections. The sizable NNLO corrections for distributions are largely caused by the broader energy flow inside jets at NNLO and are to be expected generally for processes with jets at LO.

   hep-phPRD(2017)·22 citations
8. 08*

   Natural Alignment in the Two Higgs Doublet Model

   P. S. Bhupal Dev🇺🇸 · Apostolos Pilaftsis🇬🇧

   As the LHC Higgs data persistently suggest the couplings of the observed 125 GeV Higgs boson to be consistent with the Standard Model (SM) expectations, any extended Higgs sector must lead to the so-called SM alignment limit, where one of the Higgs bosons behaves exactly like that of the SM. In the context of the Two Higgs Doublet Model (2HDM), this alignment is often associated with either decoupling of the heavy Higgs sector or accidental cancellations in the 2HDM potential. We present a novel symmetry justification for `natural' alignment without necessarily decoupling or fine-tuning. We show that there exist only three different symmetry realizations of the natural alignment scenario in 2HDM. We identify the 2HDM parameter space satisfying the natural alignment condition up to the Planck scale. We also analyze new collider signals for the heavy Higgs sector in the natural alignment limit, which dominantly lead to third-generation quarks in the final state and can serve as a useful observational tool during the Run-II phase of the LHC.

   hep-phhep-exJ.Phys.Conf.Ser.(2017)·24 citations
9. 09*

   A unitarity compatible approach to one-loop amplitudes with massive fermions

   Simon Badger🇬🇧 · Christian Brønnum-Hansen🇬🇧 · Francesco Buciuni🇬🇧 · Donal O'Connell🇬🇧

   We explain how one-loop amplitudes with massive fermions can be computed using only on-shell information. We first use the spinor-helicity formalism in six dimensions to perform generalised unitarity cuts in $d$ dimensions. We then show that divergent wavefunction cuts can be avoided, and the remaining ambiguities in the renormalised amplitudes can be fixed, by matching to universal infrared poles in $4-2ϵ$ dimensions and ultraviolet poles in $6-2ϵ$ dimensions. In the latter case we construct an effective Lagrangian in six dimensions and reduce the additional constraint to an on-shell tree-level computation.

   hep-phhep-thJHEP(2017)·23 citations
10. 10*

    Tagging new physics with charm

    Sho Iwamoto🇮🇱 · Gabriel Lee🇮🇱 · Yael Shadmi🇮🇱 · Yaniv Weiss🇮🇱

    We propose a new variable, the charm fraction, for collider searches for new physics. We analyze this variable in the context of searches for simplified supersymmetry models with squarks, the gluino, and the bino, assuming that only the lightest mass-degenerate squarks can be produced at the high-luminosity LHC. The charm fraction complements event counting and kinematic information, increasing the sensitivity of the searches for models with heavy gluinos, for which squark production is flavor-blind. If squarks are discovered at the LHC, this variable can help discriminate between different underlying models. In particular, with improved charm tagging, the charm fraction can provide information on the gluino mass, and in some scenarios, on whether this mass is within the reach of a future 100 TeV hadron collider.

    hep-phhep-exJHEP(2017)·4 citations
11. 11*

    CP-odd invariants for multi-Higgs models and applications with discrete symmetry

    Ivo de Medeiros Varzielas🇵🇹

    CP-odd invariants are useful for studying the CP properties of Lagrangians in any basis. We explain how to build basis invariants for the scalar sector, and how to distinguish CP-odd invariants from CP-even invariants. Up to a certain order, we use these methods to systematically build all the CP-odd invariants. The CP-odd invariants signal either explicit or spontaneous violation of CP. Making use of the CP-odd invariants, we determine the CP properties of potentials with 3 and with 6 Higgs fields arranged as triplets of specific discrete symmetries in the $\Delta (3n^2)$ or $\Delta (6n^2)$ series (inlcuding $A_4$, $S_4$, $\Delta (27)$ and $\Delta (54)$ as well as the cases for $n>3$).

    hep-phJ.Phys.Conf.Ser.(2017)·1 citation
12. 12*

    $\varphi$ meson mass and decay width in nuclear matter and nuclei

    J.J. Cobos-Martínez🇲🇽 · K. Tsushima🇧🇷 · G. Krein🇧🇷 · A.W.Thomas🇦🇺

    The mass and decay width of the $\varphi$ meson in cold nuclear matter are computed in an effective Lagrangian approach. The medium dependence of these properties are obtained by evaluating kaon-antikaon loop contributions to the $\varphi$ self-energy, employing the medium-modified kaon masses, calculated using the quark-meson coupling model. The loop integral is regularized with a dipole form factor, and the sensitivity of the results to the choice of cutoff mass in the form factor is investigated. At normal nuclear matter density we find a downward shift of the $\varphi$ mass by a few percent, while the decay width is enhanced by an order of magnitude. For a large variation of the cutoff mass parameter, the results for the $\varphi$ mass and the decay width turn out to vary very little. Our results support results in the literature which suggest that one should observe a small downward mass shift and a large broadening of the decay width. In order to explore the possibility of studying the binding and absorption of $\varphi$ mesons in nuclei, we also present the single-particle binding energies and half-widths of $\varphi$-nucleus bound states for some selected nuclei.

    ↳ nucl-thhep-exhep-phnucl-exPLB(2017)·48 citations
13. 13*

    Hairs of discrete symmetries and gravity

    Kang Sin Choi🇰🇷 · Jihn E. Kim🇰🇷 · Bumseok Kyae🇰🇷 · Soonkeon Nam🇰🇷

    Gauge symmetries are known to be respected by gravity because gauge charges carry flux lines, but global charges do not carry flux lines and are not conserved by gravitational interaction. For discrete symmetries, they are spontaneously broken in the Universe, forming domain walls. Since the realization of discrete symmetries in the Universe must involve the vacuum expectation values of Higgs fields, a string-like configuration (hair) at the intersection of domain walls in the Higgs vacua can be realized. Therefore, we argue that discrete charges are also respected by gravity.

    ↳ hep-thgr-qchep-phPLB(2017)·6 citations
14. 14*

    Maximal symmetry and mass generation of Dirac fermions and gravitational gauge field theory in six-dimensional spacetime

    Yue-Liang Wu🇨🇳

    The relativistic Dirac equation in four-dimensional spacetime reveals a coherent relation between the dimensions of spacetime and the degrees of freedom of fermionic spinors. A massless Dirac fermion generates new symmetries corresponding to chirality spin and charge spin as well as conformal scaling transformations. With the introduction of intrinsic W-parity, a massless Dirac fermion can be treated as a Majorana-type or Weyl-type spinor in a six-dimensional spacetime that reflects the intrinsic quantum numbers of chirality spin. A generalized Dirac equation is obtained in the six-dimensional spacetime with a maximal symmetry. Based on the framework of gravitational quantum field theory proposed in Ref. \cite{YLWU} with the postulate of gauge invariance and coordinate independence, we arrive at a maximally symmetric gravitational gauge field theory for the massless Dirac fermion in six-dimensional spacetime. Such a theory is governed by the local spin gauge symmetry SP(1,5) and the global Poincaré symmetry P(1,5)= SO(1,5)$⋉P^{1,5}$ as well as the charge spin gauge symmetry SU(2). The theory leads to the prediction of doubly electrically charged bosons. A scalar field and conformal scaling gauge field are introduced to maintain both global and local conformal scaling symmetries. A generalized gravitational Dirac equation for the massless Dirac fermion is derived in the six-dimensional spacetime. The equations of motion for gauge fields are obtained with conserved currents in the presence of gravitational effects. The dynamics of the gauge-type gravifield as a Goldstone-like boson is shown to be governed by a conserved energy-momentum tensor, and its symmetric part provides a generalized Einstein equation of gravity. An alternative geometrical symmetry breaking mechanism for the mass generation of Dirac fermions is demonstrated.

    ↳ hep-thgr-qchep-phCPC(2017)·3 citations
15. 15*

    Lectures on the Infrared Structure of Gravity and Gauge Theory

    Andrew Strominger🇺🇸

    This is a redacted transcript of a course given by the author at Harvard in spring semester 2016. It contains a pedagogical overview of recent developments connecting the subjects of soft theorems, the memory effect and asymptotic symmetries in four-dimensional QED, nonabelian gauge theory and gravity with applications to black holes. The lectures may be viewed online at https://goo.gl/3DJdOr. Please send typos or corrections to strominger@physics.harvard.edu.

    ↳ hep-thastro-ph.HEgr-qchep-ph+21172 citations
16. 16*

    Nonperturbative comparison of clover and HISQ quarks in lattice QCD and the properties of the phi meson

    Bipasha Chakraborty🇬🇧 · C. T. H. Davies🇬🇧 · G. C. Donald🇩🇪 · J. Koponen🇬🇧 · G. P. Lepage🇺🇸

    We compare correlators for pseudoscalar and vector mesons made from valence strange quarks using the clover quark and highly improved staggered quark (HISQ) formalisms in full lattice QCD. We use fully nonperturbative methods to normalise vector and axial vector current operators made from HISQ quarks, clover quarks and from combining HISQ and clover fields. This allows us to test expectations for the renormalisation factors based on perturbative QCD, with implications for the error budget of lattice QCD calculations of the matrix elements of clover-staggered $b$-light weak currents, as well as further HISQ calculations of the hadronic vacuum polarisation. We also compare the approach to the (same) continuum limit in clover and HISQ formalisms for the mass and decay constant of the $\varphi$ meson. Our final results for these parameters, using single-meson correlators and neglecting quark-line disconnected diagrams are: $m_{\varphi }=$ 1.023(6) GeV and $f_{\varphi }=$ 0.238(3) GeV in good agreement with experiment. The results come from calculations in the HISQ formalism using gluon fields that include the effect of $u$, $d$, $s$ and $c$ quarks in the sea with three lattice spacing values and $m_{u/d}$ values going down to the physical point.

    ↳ hep-lathep-phPRD(2017)·28 citations
17. 17*

    Perturbative unitarity of Lee-Wick quantum field theory

    Damiano Anselmi🇮🇹 · Marco Piva🇮🇹

    We study the perturbative unitarity of the Lee-Wick models, formulated as nonanalytically Wick rotated Euclidean theories. The complex energy plane is divided into disconnected regions and the values of a loop integral in the various regions are related to one another by a nonanalytic procedure. We show that the one-loop diagrams satisfy the expected, unitary cutting equations in each region: only the physical degrees of freedom propagate through the cuts. The goal can be achieved by working in suitable subsets of each region and proving that the cutting equations can be analytically continued as a whole. We make explicit calculations in the cases of the bubble and triangle diagrams and address the generality of our approach. We also show that the same higher-derivative models violate unitarity if they are formulated directly in Minkowski spacetime.

    ↳ hep-thhep-phmath-phmath.MPPRD(2017)·136 citations
18. 18*

    From lepton interactions to hadron and nuclear ones at high multiplicity

    V. Dunin🇷🇺 · E. Kokoulina🇷🇺 · M. Nevmerzhitsky🇧🇾 · V. Nikitin🇷🇺 · Yu. Petukhov🇷🇺 · V. Riadovikov🇷🇺 · I. Roufanov🇷🇺 · V. Volkov🇷🇺 · A. Vorobiev🇷🇺

    Multiplicity data up to 200 GeV in e+e- annihilation are described well by the two-stage model based on pQCD and suggested the phenomenological scheme of hadronization. This model confirms the fragmentation mechanism of hadronization (in vacuum). It allows to estimate mean multiplicity at 500 GeV and 1 TeV. Gluon dominance model is the modification of this model for the description of hadronic interactions. It was realised by an inclusion of gluons. It demonstrates very strong evidence of the recombination mechanism of hadronization. In this case, the mean multiplicity of hadrons formed from a single gluon grows with energy and it exceeds the corresponding values for lepton interactions. At the same time, the region of high multiplicity is stipulated for splitting of active gluons. The excess of soft photon yield is experimentally confirmed at Nuclotron (JINR) in the interactions of the 3.5A GeV/c deuteron and lithium beams with the carbon target.

    ↳ hep-exhep-phPoS(2016)·0 citations
19. 19*

    One-electron atoms in screened modified gravity

    Leong Khim Wong🇬🇧 · Anne-Christine Davis🇬🇧

    In a large class of scalar-tensor theories that are potential candidates for dark energy, a nonminimal coupling between the scalar and the photon is possible. The presence of such an interaction grants us the exciting prospect of directly observing dark sector phenomenology in the electromagnetic spectrum. This paper investigates the behavior of one-electron atoms in this class of modified gravity models, exploring their viability as probes of deviations from general relativity in both laboratory and astrophysical settings. Building heavily on earlier studies, our main contribution is threefold: A thorough analysis finds additional fine-structure corrections previously unaccounted for, which now predict a contribution to the Lamb shift that is larger by nearly 4 orders of magnitude. In addition, they also predict a scalar-mediated photon-photon interaction, which now constrains the scalar's coupling to the photon independently of the matter coupling. This was not previously possible with atomic precision tests. Our updated constraints are ${\log }_{10}{\beta }_m\lesssim 13.4$ and ${\log }_{10}{\beta }_{\gamma }\lesssim 19.0$ for the matter and photon coupling, respectively, although these remain uncompetitive with bounds from other experiments. Second, we include the effects of the nuclear magnetic moment, allowing for the study of hyperfine structure and the 21 cm line, which hitherto have been unexplored in this context. Finally, we also examine how a background scalar leads to equivalence principle violations.

    ↳ astro-ph.COhep-phPRD(2017)·8 citations
20. 20*

    A Course in Amplitudes

    Tomasz R. Taylor🇵🇱

    This a pedagogical introduction to scattering amplitudes in gauge theories. It proceeds from Dirac equation and Weyl fermions to the two pivot points of current developments: the recursion relations of Britto, Cachazo, Feng and Witten, and the unitarity cut method pioneered by Bern, Dixon, Dunbar and Kosower. In ten lectures, it covers the basic elements of on-shell methods.

    ↳ hep-thhep-phPhys.Rept.(2017)·41 citations
21. 21*

    Spontaneous symmetry breaking and the Unruh effect

    Antonio Dobado🇪🇸

    In this work we consider the ontological status of the Unruh effect. Is it just a formal mathematical result? Or the temperature detected by an accelerating observer can lead to real physical effects such as phase transition. In order to clarify this issue we use the Thermalization Theorem to explore the possibility of having a restoration of the symmetry in a system with spontaneous symmetry breaking of an internal continuous symmetry as seen by an accelerating observer. We conclude that the Unruh effect is an ontic effect, rather than an epistemic one, giving rise, in the particular example considered here, to a phase transition (symmetry restoration) in the region close to the accelerating observer horizon.

    ↳ gr-qchep-phhep-th3 citations
22. 22*

    Recommendations of the LHC Dark Matter Working Group: Comparing LHC searches for heavy mediators of dark matter production in visible and invisible decay channels

    Andreas Albert🇩🇪 · Mihailo Backovic🇧🇪 · Antonio Boveia🇺🇸 · Oliver Buchmueller🇬🇧 · Giorgio Busoni🇦🇺 · Albert De Roeck🇨🇭 · Caterina Doglioni🇸🇪 · Tristan DuPree🇳🇱 · Malcolm Fairbairn🇬🇧 · Marie-Helene Genest🇫🇷 · Stefania Gori🇺🇸 · Giuliano Gustavino🇮🇹 and 18 other authors

    Weakly-coupled TeV-scale particles may mediate the interactions between normal matter and dark matter. If so, the LHC would produce dark matter through these mediators, leading to the familiar "mono-X" search signatures, but the mediators would also produce signals without missing momentum via the same vertices involved in their production. This document from the LHC Dark Matter Working Group suggests how to compare searches for these two types of signals in case of vector and axial-vector mediators, based on a workshop that took place on September 19/20, 2016 and subsequent discussions. These suggestions include how to extend the spin-1 mediated simplified models already in widespread use to include lepton couplings. This document also provides analytic calculations of the relic density in the simplified models and reports an issue that arose when ATLAS and CMS first began to use preliminary numerical calculations of the dark matter relic density in these models.

    ↳ hep-exastro-ph.COhep-phPhys.Dark Univ.(2019)·212 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.