HEP Phenomenology·hep-ph

Wed·Oct 4, 2017Wednesday·October 4, 2017

23 papers—14 primary·9 cross-listed·reconstructed*

01*
Bounding Quantum Dark Forces
Philippe Brax🇫🇷 · Sylvain Fichet🇧🇷 · Guillaume Pignol🇫🇷
Dark sectors lying beyond the Standard Model and containing sub-GeV particles which are bilinearly coupled to nucleons would induce quantum forces of the Casimir-Polder type in ordinary matter. Such new forces can be tested by a variety of experiments over many orders of magnitude. We provide a generic interpretation of these experimental searches and apply it to a sample of forces from dark scalars behaving as $1/ r^{3}$ , $1/ r^{5}$ , $1/ r^{7}$ at short range. The landscape of constraints on such quantum forces differs from the one of modified gravity with Yukawa interactions, and features in particular strong short-distance bounds from molecular spectroscopy and neutron scattering.
hep-phPRD(2018)·73 citations
02*
Vectorlike Particles, $Z^{'}$ and Yukawa Unification in F-theory inspired $E_{6}$
Athanasios Karozas🇬🇷 · George K. Leontaris🇬🇷 · Qaisar Shafi🇺🇸
We explore the low energy implications of an F-theory inspired $E_{6}$ model whose breaking yields, in addition to the MSSM gauge symmetry, a $Z^{'}$ gauge boson associated with a $U (1)$ symmetry broken at the TeV scale. The zero mode spectrum of the effective low energy theory is derived from the decomposition of the $27$ and $27$ representations of $E_{6}$ and we parametrise their multiplicities in terms of a minimum number of flux parameters. We perform a two-loop renormalisation group analysis of the gauge and Yukawa couplings of the effective theory model and estimate lower bounds on the new vectorlike particles predicted in the model. We compute the third generation Yukawa couplings in an F-theory context assuming an $E_{8}$ point of enhancement and express our results in terms of the local flux densities associated with the gauge symmetry breaking. We find that their values are compatible with the ones computed by the renormalisation group equations, and we identify points in the parameter space of the flux densities where the $t - b - τ$ Yukawa couplings unify.
hep-phhep-thPLB(2018)·3 citations
03*
New results from a number operator interpretation of the compositeness of bound and resonant states
J.A. Oller🇪🇸
A novel theoretical approach to the problem of the compositeness ( $X$ ) of a resonance or bound state is developed on the basis of the expectation values of the number operators of the free particles in the continuum. This formalism is specially suitable for effective field theories in which the bare elementary states are integrated out but that give rise to resonance and bound states when implemented in nonperturbative calculations. We demonstrate that $X = 1$ for finite-range energy-independent potentials, either regular or singular. A non-trivial example for an energy-dependent potential is discussed where it is shown that $X$ is independent of any type of cutoff regulator employed. The generalization of these techniques to relativistic states is developed. We also explain how to obtain a meaningful compositeness with respect to the open channels for resonances, even if it is complex in a first turn, by making use of suitable phase-factor transformations. Defining elementariness as $X = 0$ , we derive a new universal criterion for the elementariness of a bound state. Along the same lines, a necessary condition for a resonance to be qualified as elementary is given. The application of the formalism here developed might be of considerable practical interest.
hep-phhep-lathep-thnucl-thAnnals Phys.(2018)·59 citations
04*
Scheming in the SMEFT
Ilaria Brivio🇩🇰
We discuss the constraints on the Standard Model Effective Field Theory inferred from global fits to electroweak data. Special attention is paid to two unconstrained combinations of Wilson coefficients that are present when the analysis is restricted to measurements of $ψ ˉ ψ \to ψ ˉ ψ$ scatterings. We illustrate how these unconstrained directions arise due to a reparameterization invariance that characterizes $ψ ˉ ψ \to ψ ˉ ψ$ processes but is not respected in $ψ ˉ ψ \to ψ ˉ ψ ψ ˉ ψ$ scatterings. This invariance is independent of the operator basis adopted and of the choice of the input parameters. This is verified comparing the results obtained in the { $α^_{e m}, m^_{Z}, G^_{F}$ } input scheme with those of a { $m^_{W}, m^_{Z}, G^_{F}$ } scheme.
hep-phPoS(2017)·2 citations
05*
The Neutrino Option
Ilaria Brivio🇩🇰
We discuss the possibility that the Higgs potential and electroweak scale are generated radiatively in a type-I seesaw scenario. A Higgs potential consistent with experimental constraints can be obtained in this hypothesis for a Majorana mass scale $m_{N} \sim 10 - 500$ PeV and with neutrino Yukawa couplings of order $∣ ω ∣ \sim 1 0^{- 4.5} - 1 0^{- 6}$ . Remarkably, neutrino masses and mixings can be simultaneously accommodated within this parameter space. This framework, that ties together Higgs phenomenology, precision top quark mass measurements and neutrino physics, represents an alternative approach to the hierarchy problem, in which the Higgs mass is not stabilized around the TeV scale, but rather determined by radiative corrections at higher energies. Traditional hurdles in overcoming the hierarchy problem are then traded for the new challenge of generating PeV Majorana masses while suppressing the tree-level scalar potential in the UV.
hep-phPoS(2017)·0 citations
06*
Entropy and Multifractality in Relativistic Ion-Ion Collisions
Shaista Khan🇮🇳 · Shakeel Ahmad🇮🇳
Entropy production in multiparticle systems is investigated by analysing the experimental data on ion-ion collision at AGS and SPS energies and comparing the findings with those reported earlier for hadron-hadron, hadron-nucleus and nucleus-nucleus collisions. It is observed that the entropy produced in limited and full phase space, when normalised to maximum rapidity exhibits a kind of scaling which is nicely supported by Monte Carlo model \hij. Using the Rényi's order-q information entropy, multifractal characteristics of particle production are examined in terms of Generalized dimensions, D $_{q}$ . Nearly the same values of multifractal specific heat, $c$ observed in hadronic and ion-ion collisions over a wide range of incident energies suggest that the quantity $c$ may be used as a universal characteristic of multiparticle production in hadron-hadron, hadron-nucleus and nucleus-nucleus collisions.
hep-phnucl-thAdv.High Energy Phys.(2018)·4 citations
07*
A multi-messenger study of the total galactic high-energy neutrino emission
G. Pagliaroli🇮🇹 · F.L. Villante🇮🇹
A detailed multi-messenger study of the high-energy emission from the Galactic plane is possible nowadays thanks to the observations provided by gamma and neutrino telescopes and could be mandatory in order to obtain a consistent scenario. We show the potential of this approach by using the total gamma flux from the inner galactic region measured by HESS at $1 TeV$ and in the longitude range $- 7 5^{\circ} < l < 6 0^{\circ}$ . By comparing the observational data with the expected diffuse galactic emission, we highlight the existence of an extended hot region of the gamma sky where the cumulative sources contribution dominates over the diffuse component. This region approximately coincides with the portion of the galactic plane from which a $\sim 2 σ$ excess of showers is observed in IceCube high energy starting events. In the assumption that hadronic mechanisms are responsible for the observed gamma emission, we estimate the total galactic contribution (i.e. including both diffuse and the source components) to the IceCube neutrino signal as a function of the spectral index and energy cutoff of the sources, taking also into account the upper limit on a galactic component provided by Antares.
hep-phastro-ph.HEJCAP(2018)·14 citations
08*
Pursuit for optimal baseline for matter nonstandard interactions in long baseline neutrino oscillation experiments
Timo J. Kärkkäinen🇫🇮
We investigate the prospects for probing the strength of the possible matter nonstandard neutrino interactions (mNSI) in long baseline neutrino oscillation experiments and the interference of the leptonic CP angle $δ_{C P}$ with the constraining of the mNSI couplings. The interference is found to be strong in the case of the $ν_{e} \leftrightarrow ν_{μ}$ and $ν_{e} \leftrightarrow ν_{τ}$ transitions but not significant in the other cases. We use SPS and DUNE setups as benchmarks.
hep-ph1 citation
09*
Supersymmetric Gauged B-L Model of Dark Matter and Fine Tuning
Luigi Delle Rose🇬🇧 · Shaaban Khalil🇪🇬 · Simon J. D. King🇬🇧 · Carlo Marzo🇪🇪 · Stefano Moretti🇬🇧 · Cem S. Un🇹🇷
We investigate how the Fine-Tuning (FT) in the B-L Supersymmetric Standard Model (BLSSM) compares to the Minimally Supersymmetric Standard Model (MSSM), where both models have universality. This is done for two scales: both low (i.e. collider) and high (i.e. Grand Unified Theory (GUT)) scales. We see this is similar for both models and the two scale regimes. We also study the possible Dark Matter (DM) candidates each model offers in a realistic scenario satisfying relic density constraints. Our findings are that whilst the parameter space for the single MSSM DM candidate is severely constrained, the BLSSM offers multiple candidates in a much wider region.
hep-phPoS(2017)·4 citations
10*
Supersymmetric signals in Z' decays
Gennaro Corcella🇮🇹
I present a scenario wherein heavy neutral vector bosons Z', predicted by GUT-inspired U(1)' models, decay into supersymmetric final states, besides the Standard Model channels investigated at the LHC. It is found that accounting for such decays lowers the exclusion limits on the Z' mass at 13 TeV by about 200-300 GeV.
hep-phPoS(2018)·0 citations
11*
Implications of strict gauge invariance for particle spectra and precision observables
Axel Maas🇦🇹 · Larissa Egger🇦🇹
The discovery of the Higgs together with the excellent performance of the LHC allow to make precision tests of Brout-Englert-Higgs Physics, and especially its underlying field-theory. In this field theory strict gauge-invariance requires observable states to have a more involved structure than assumed in standard perturbation theory. This can lead to, likely rather very small, deviations in precision tests of the standard model. Here, the mechanism behind these deviations will be elucidated, and, as an example, its possible implications for the R ratio at future linear colliders will be estimated.
hep-phPoS(2017)·3 citations
12*
Shannon entropy and hadronic decays
Felipe J. Llanes-Estrada (presenter)🇪🇸 · Pedro Carrasco Millán🇪🇸 · Ana Porras Riojano🇪🇸 · Esteban M. Sánchez García (Univ. Madrid, Complutense)🇪🇸 · M. Ángeles García Ferrero (ICMAT, Madrid)🇪🇸
How much information is added to the Review of Particle Physics when a new decay branching ratio of a hadron is measured and reported? This is quantifiable by Shannon's information entropy $S (i) = - \sum_{f} B R_{(i ⟶ f)} lo g B R_{(i ⟶ f)}$ that takes as input the experimental branching ratios (BR) of the decay distribution of particle i. It may be used at two levels, against the distribution of decay-channel probabilities, or against the distribution of individual quantum-state probabilities (integrating the phase space of those states provides the former). We illustrate the concept with some examples.
hep-phPoS(2017)·5 citations
13*
Novel Jet Observables from Machine Learning
Kaustuv Datta🇺🇸 · Andrew J. Larkoski🇺🇸
Previous studies have demonstrated the utility and applicability of machine learning techniques to jet physics. In this paper, we construct new observables for the discrimination of jets from different originating particles exclusively from information identified by the machine. The approach we propose is to first organize information in the jet by resolved phase space and determine the effective $N$ -body phase space at which discrimination power saturates. This then allows for the construction of a discrimination observable from the $N$ -body phase space coordinates. A general form of this observable can be expressed with numerous parameters that are chosen so that the observable maximizes the signal vs.~background likelihood. Here, we illustrate this technique applied to discrimination of $H \to b b ˉ$ decays from massive $g \to b b ˉ$ splittings. We show that for a simple parametrization, we can construct an observable that has discrimination power comparable to, or better than, widely-used observables motivated from theory considerations. For the case of jets on which modified mass-drop tagger grooming is applied, the observable that the machine learns is essentially the angle of the dominant gluon emission off of the $b b ˉ$ pair.
hep-phhep-exJHEP(2018)·70 citations
14*
Two Top Utilities of Two Higgs Doublets: Electroweak Baryogenesis and Alignment
George W.-S. Hou🇦🇺
With two Higgs doublets but without any discrete $Z_{2}$ symmetry to forbid flavor changing neutral Higgs couplings, new top Yukawa couplings $ρ_{tt}$ and $ρ_{t c}$ are allowed and naturally complex. Electroweak baryogenesis is remarkably efficient if both $ρ_{tt}$ (and $ρ_{t c}$ ) and exotic Higgs quartic couplings are $O (1)$ . Furthermore, the alignment phenomenon, that the observed 125 GeV boson so closely resembles the Standard Model Higgs boson, emerges naturally. One not only has many new flavor and CPV phenomena (modulo SM-like flavor organization plus alignment), but the exotic Higgs bosons $H^{0}$ , $A^{0}$ and $H^{+}$ are necessarily sub-TeV in mass, and LHC search should be readjusted.
hep-ph0 citations
15*
Exciting Nucleons in Compton Scattering and Hydrogen-Like Atoms
Franziska Hagelstein (JGU Mainz)🇩🇪
This PhD thesis is devoted to the low-energy structure of the nucleon (proton and neutron) as seen through electromagnetic probes, e.g., electron and Compton scattering. The research presented here is based primarily on dispersion theory and chiral effective-field theory. The main motivation is the recent proton radius puzzle, which is the discrepancy between the classic proton charge radius determinations (based on electron-proton scattering and normal hydrogen spectroscopy) and the highly precise extraction based on first muonic-hydrogen experiments by the CREMA Collaboration. The precision of muonic-hydrogen experiments is presently limited by the knowledge of proton structure effects beyond the charge radius. A major part of this thesis is devoted to calculating these effects using everything we know about the nucleon electromagnetic structure from both theory and experiment. The thesis consists of eight chapters. The first and last are, respectively, the introduction and conclusion. The remainder of this thesis can roughly be divided into the following three topics: finite-size effects in hydrogen-like atoms, real and virtual Compton scattering, and two-photon-exchange effects.
↳ nucl-thhep-phnucl-exphysics.atom-ph12 citations
16*
Dynamical initial state model for relativistic heavy-ion collisions
Chun Shen🇺🇸 · Björn Schenke🇺🇸
We present a fully three-dimensional model providing initial conditions for energy and net-baryon density distributions in heavy ion collisions at arbitrary collision energy. The model includes the dynamical deceleration of participating nucleons or valence quarks, depending on the implementation. The duration of the deceleration continues until the string spanned between colliding participants is assumed to thermalize, which is either after a fixed proper time, or a fluctuating time depending on sampled final rapidities. Energy is deposited in space-time along the string, which in general will span a range of space-time rapidities and proper times. We study various observables obtained directly from the initial state model, including net-baryon rapidity distributions, 2-particle rapidity correlations, as well as the rapidity decorrelation of the transverse geometry. Their dependence on the model implementation and parameter values is investigated. We also present the implementation of the model with 3+1 dimensional hydrodynamics, which involves the addition of source terms that deposit energy and net-baryon densities produced by the initial state model at proper times greater than the initial time for the hydrodynamic simulation.
↳ nucl-thhep-phnucl-exPRC(2018)·221 citations
17*
Inconsistencies in Verlinde's emergent gravity
De-Chang Dai🇨🇳 · Dejan Stojkovic🇺🇸
We point out that recent Verlinde's proposal of emergent gravity suffers from some internal inconsistencies. The main idea in this proposal is to preserve general relativity at short scales where numerous tests verified its validity, but modify it on large scales where we meet puzzles raised by observations (in particular dark matter), by using some entropic concepts. We first point out that gravity as a conservative force is very difficult (if possible at all) to portray as an entropic force. We then show that the derivation of the MOND relation using the elastic strain idea is not self-consistent. When properly done, Verlinde's elaborate procedure recovers the standard Newtonian gravity instead of MOND.
↳ gr-qchep-phhep-thJHEP(2017)·30 citations
18*
Search for vector mediator of Dark Matter production in invisible decay mode
NA64 Collaboration: D. Banerjee🇨🇭 · V. E. Burtsev🇷🇺 · A. G. Chumakov🇷🇺 · D. Cooke🇨🇭 · P. Crivelli🇨🇭 · E. Depero🇨🇭 · A. V. Dermenev🇷🇺 · S. V. Donskov🇷🇺 · F. Dubinin🇨🇭 · R. R. Dusaev🇷🇺 · S. Emmenegger🇨🇭 · A. Fabich🇨🇭 and 31 other authors
A search is performed for a new sub-GeV vector boson ( $A^{'}$ ) mediated production of Dark Matter ( $χ$ ) in the fixed-target experiment, NA64, at the CERN SPS. The $A^{'}$ , called dark photon, could be generated in the reaction $e^{-} Z \to e^{-} Z A^{'}$ of 100 GeV electrons dumped against an active target which is followed by the prompt invisible decay $A^{'} \to χ χ$ . The experimental signature of this process would be an event with an isolated electron and large missing energy in the detector. From the analysis of the data sample collected in 2016 corresponding to $4.3 \times 1 0^{10}$ electrons on target no evidence of such a process has been found. New stringent constraints on the $A^{'}$ mixing strength with photons, $1 0^{- 5} ≲ ϵ ≲ 1 0^{- 2}$ , for the $A^{'}$ mass range $m_{A^{'}} ≲ 1$ GeV are derived. For models considering scalar and fermionic thermal Dark Matter interacting with the visible sector through the vector portal the 90% C.L. limits $1 0^{- 11} ≲ y ≲ 1 0^{- 6}$ on the dark-matter parameter $y = ϵ^{2} α_{D} (\frac{m _{χ}}{m _{A^{'}}})^{4}$ are obtained for the dark coupling constant $α_{D} = 0.5$ and dark-matter masses $0.001 ≲ m_{χ} ≲ 0.5$ GeV. The lower limits $α_{D} ≳ 1 0^{- 3}$ for pseudo-Dirac Dark Matter in the mass region $m_{χ} ≲ 0.05$ GeV are more stringent than the corresponding bounds from beam dump experiments. The results are obtained by using tree level, exact calculations of the $A^{'}$ production cross-sections, which turn out to be significantly smaller compared to the one obtained in the Weizsäcker-Williams approximation for the mass region $m_{A^{'}} ≳ 0.1$ GeV.
↳ hep-exhep-phPRD(2018)·193 citations
19*
Universal strangeness production and size fluctuactions in small and large systems
P.Castorina🇮🇹 · M.Floris🇨🇭 · S.Plumari🇮🇹 · H.Satz🇩🇪
Strangeness production in high multiplicity events gives indications on the transverse size fluctuactions in nucleus-nucleus ( $AA$ ), proton-nucleus ( $p A$ ) and proton-proton ( $pp$ ) collisions. In particular the behavior of strange particle hadronization in "small" ( $pp, p A$ ) and "large" ( $AA$ ) initial configurations of the collision can be tested for the specific particle species, for different centralities and for large fluctuations of the transverse size in $p A$ and $pp$ by using the recent ALICE data. A universality of strange hadron production emerges by introducing a dynamical variable proportional to the initial parton density in the transverse plane.
↳ nucl-thhep-phPoS(2017)·2 citations
20*
Transverse expansion of hot magnetized Bjorken flow in heavy ion collisions
M. Haddadi Moghaddam🇮🇷 · B. Azadegan🇮🇷 · A. F. Kord🇮🇷 · W. M. Alberico🇮🇹
We argue that the existence of an inhomogeneous external magnetic field can lead to radial flow in transverse plane. Our aim is to show how the introduction of a magnetic field generalizes the Bjorken flow. We investigate the effect of an inhomogeneous weak external magnetic field on the transverse expansion of in-viscid fluid created in high energy nuclear collisions. In order to simplify our calculation and compare with Gubser model, we consider the fluid under investigation to be produced in central collisions, at small impact parameter; azimuthal symmetry has been considered. In our model, we assume an inhomogeneous external magnetic field following the power-law decay in proper time and having radial inhomogeneity perpendicular to the radial velocity of the in-viscid fluid in the transverse plane; then the space time evolution of the transverse expansion of the fluid is obtained. We also show how the existence of an inhomogeneous external magnetic field modifies the energy density. Finally we use the solutions for the transverse velocity and energy density in the presence of a weak magnetic field, to estimate the transverse momentum spectrum of protons and pions emerging from the Magneto-hydrodynamic solutions.
↳ nucl-thhep-phEPJC(2019)·4 citations
21*
Consistent description of field theories with non-Hermitian mass terms
Jean Alexandre🇬🇧 · Peter Millington🇬🇧 · Dries Seynaeve🇬🇧
We review how to describe a field theory that includes a non-Hermitian mass term in the region of parameter space where the Lagrangian is $P T$ -symmetric. The discrete symmetries of the system are essential for understanding the consistency of the model, and the link between conserved current and variation of the Lagrangian has to be revisited in the case of continuous symmetries.
↳ hep-thhep-phJ.Phys.Conf.Ser.(2018)·18 citations
22*
Symmetry Properties of Nonlocal Quark Bilinear Operators on a Lattice
Jiunn-Wei Chen🇹🇼 · Tomomi Ishikawa🇨🇳 · Luchang Jin🇺🇸 · Huey-Wen Lin🇺🇸 · Jian-Hui Zhang🇩🇪 · Yong Zhao🇺🇸
Using symmetry properties, we determine the mixing pattern of a class of nonlocal quark bilinear operators containing a straight Wilson line along a spatial direction. We confirm the previous study that mixing among the lowest dimensional operators, which have mass dimension equals three, can occur if chiral symmetry is broken in the lattice action. For higher dimensional operators, we find that the dimension three operators will always mix with dimension four operators even if chiral symmetry is preserved. Also, the number of dimension four operators involved in the mixing is large hence it is impractical to remove the mixing by the improvement procedure. Our result is important to determining the Bjorken- $x$ dependence parton distribution functions using the quasi-distribution method on a Euclidean lattice. The requirement of using large hadron momentum in this approach makes the control of errors from dimension four operators even more important.
↳ hep-lathep-phCPC(2019)·81 citations
23*
Event patterns extracted from anisotropic spectra of charged particles produced in Pb-Pb collisions at 2.76 TeV
Ya-Hui Chen🇨🇳 · Fu-Hu Liu🇨🇳
Event patterns extracted from anisotropic spectra of charged particles produced in lead-lead collisions at 2.76 TeV are investigated. We use an inverse power-law resulted from the QCD calculus to describe the transverse momentum spectrum in the hard scattering process, and a revised Erlang distribution resulted from a multisource thermal model to describe the transverse momentum spectrum and anisotropic flow in the soft excitation process. The pseudorapidity distribution is described by a three-Gaussian function which is a revision of the Landau hydrodynamic model. Thus, the event patterns at the kinetic freeze-out are displayed by the scatter plots of the considered particles in the three-dimensional velocity, momentum, and rapidity spaces.
↳ nucl-thhep-exhep-phnucl-exEPJA(2017)·4 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.