HEP Phenomenology·hep-ph

Mon·Nov 26, 2018Monday·November 26, 2018

18 papers—12 primary·6 cross-listed·reconstructed*

01*
Weighing the Solar Axion
Theopisti Dafni🇪🇸 · Ciaran A. J. O'Hare🇪🇸 · Biljana Lakić🇭🇷 · Javier Galán🇪🇸 · Francisco J. Iguaz🇪🇸 · Igor G. Irastorza🇪🇸 · Krešimir Jakovčić🇭🇷 · Gloria Luzón🇪🇸 · Javier Redondo🇪🇸 · Elisa Ruiz Chóliz🇪🇸
Axion helioscopes search for solar axions and axion-like particles via inverse Primakoff conversion in strong laboratory magnets pointed at the Sun. While helioscopes can always measure the axion coupling to photons, the conversion signal is independent of the mass for axions lighter than around 0.02 eV. Masses above this value on the other hand have suppressed signals due to axion-photon oscillations which destroy the coherence of the conversion along the magnet. However, the spectral oscillations present in the axion conversion signal between these two regimes are highly dependent on the axion mass. We show that these oscillations are observable given realistic energy resolutions and can be used to determine the axion mass to within percent level accuracies. Using projections for the upcoming helioscope IAXO, we demonstrate that $> 3 σ$ sensitivity to a non-zero axion mass is possible between $3 \times 1 0^{- 3}$ and $1 0^{- 1}$ eV for both the Primakoff and axion-electron solar fluxes.
hep-phastro-ph.COPRD(2019)·53 citations
02*
The electron self-energy in QED at two loops revisited
Ina Hönemann🇩🇪 · Kirsten Tempest🇩🇪 · Stefan Weinzierl🇩🇪
We reconsider the two-loop electron self-energy in quantum electrodynamics. We present a modern calculation, where all relevant two-loop integrals are expressed in terms of iterated integrals of modular forms. As boundary points of the iterated integrals we consider the four cases $p^{2} = 0$ , $p^{2} = m^{2}$ , $p^{2} = 9 m^{2}$ and $p^{2} = \infty$ . The iterated integrals have $q$ -expansions, which can be used for the numerical evaluation. We show that a truncation of the $q$ -series to order $O (q^{30})$ gives numerically for the finite part of the self-energy a relative precision better than $1 0^{- 20}$ for all real values $p^{2} / m^{2}$ .
hep-phPRD(2018)·50 citations
03*
Field redefinitions in effective theories at higher orders
Juan Carlos Criado🇪🇸 · Manuel Perez-Victoria🇪🇸
The invariance of physical observables under redefinitions of the quantum fields is a well-known and important property of quantum field theory. We study perturbative field redefinitions in effective theories, paying special attention to higher-order effects and their impact on matching to an ultraviolet theory at the classical and quantum levels.
hep-phJHEP(2019)·117 citations
04*
Vacuum birefringence in the field of a current loop and a guided electromagnetic wave
O. Novak🇺🇦 · M. Diachenko🇺🇦 · E. Padusenko🇺🇦 · R. Kholodov🇺🇦
The effect of vacuum birefringence in a magnetic field generated by a laser-driven capacitor-coil generator as well as in field of an electromagnetic wave in a radioguide has been theoretically considered. The resulting ellipticity of a linearly polarized laser beam propagating in the considered field configuration is calculated. The obtained results are compared to the parameters of the PVLAS experiment which aims to observe the effect of magnetic vacuum birefringence experimentally.
hep-phphysics.opticsUkr.J.Phys.(2018)·3 citations
05*
Optical Potential and Removal Energies in Lepton Nucleus Scattering
Arie Bodek🇺🇸 · Tejin Cai🇺🇸
We summarize some of the results presented in arXiv:1801.07975 [nucl-th]\cite{FSIpaper}(to be published in EPJC in 2018) on modeling electron and neutrino QE scattering on a variety of nuclei within the impulse approximation. We find that with three parameters we can describe the final state lepton energy for all of available electron QE data on Lithium, Carbon+Oxygen, Aluminum, Calcium+Argon, Iron and Lead+Gold. The first parameter, the removal energy $ϵ^{P, N}$ is extracted from exclusive ee $^{'}$ p spectral function data. The second parameter $V_{e f f}$ , which accounts for the interaction of final state leptons and protons with the Coulomb potential of the nucleus, is available from published comparisons of inclusive QE electron and positron cross section. We extract the third parameter $U_{F S I} (q_{3}^{2})$ , which accounts for the interaction of the final state nucleon with the optical potential of the spectator nucleus (FSI), by fitting all available inclusive QE cross sections on nuclear targets. Here $q_{3}$ is the three momentum transfer. With these three parameters we can model the energy of final state electrons and nucleons for all available electron QE scattering data. At present the uncertainty in the value of the removal energy parameters is a the largest source of systematic error in the extraction of the neutrino oscillation parameter $Δ m^{2}$ . The use of the updated parameters in neutrino Monte Carlo generators reduces the systematic uncertainty in the combined removal energy (with FSI corrections) from $\pm$ 20 MeV to $\pm$ 5 MeV. In this short contribution we only summarize the results for Carbon+Oxygen and Calcium+Argon
hep-phhep-exnucl-exPoS(2018)·0 citations
06*
A Precision Event Generator for EW Corrections in Hadron Scattering: $KK$ MC-hh
B.F.L. Ward (1)🇺🇸 · S. Jadach (2)🇵🇱 · Z. Was (2)🇵🇱 · S.A. Yost (3) ((1) Baylor University, Waco, TX, USA, (2) Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, Poland, (3) The Citadel, Charleston, SC, USA)🇺🇸
$KK$ MC-hh is a precision event-generator for Z production and decay in hadronic collisions, which applies amplitude-level resummation to both initial and final state photon radiation, including perturbative residuals exact through $O (α^{2} L)$ , together with exact $O (α)$ EW matrix element corrections. We present some comparisons to other programs and results showing the effect of multi-photon radiation for cuts motivated by a recent ATLAS W mass analysis. We also show preliminary untuned comparisons of the electroweak corrections of $KK$ MC-hh to those of HORACE, which includes exact $O (α)$ corrections with resummed final-state photon radiation.
hep-phPoS(2019)·2 citations
07*
$Z Z$ production at the LHC: NLO QCD corrections to the loop-induced gluon fusion channel
Massimiliano Grazzini (Zurich U.)🇨🇭 · Stefan Kallweit (CERN & Milan Bicocca U.)🇮🇹 · Marius Wiesemann (CERN)🇨🇭 · Jeong Yeon Yook (Zurich U.)🇨🇭
We consider QCD radiative corrections to the production of four charged leptons in hadron collisions. We present the computation of the next-to-leading order QCD corrections to the loop-induced gluon fusion contribution. Our predictions include, for the first time, also the quark-gluon partonic channels. The computed corrections, which are formally of $O (α_{s}^{3})$ , turn out to increase the loop-induced Born-level result by an amount ranging from 75% to 71% as $s$ ranges from 8 to 13 TeV. We combine our result with state-of-the-art NNLO corrections to the quark annihilation channel, and present updated predictions for fiducial cross sections and distributions for this process.
hep-phJHEP(2019)·73 citations
08*
Impact of polarization observables and $B_{c} \to τ ν$ on new physics explanations of the $b \to c τ ν$ anomaly
Monika Blanke🇩🇪 · Andreas Crivellin🇨🇭 · Stefan de Boer🇩🇪 · Teppei Kitahara🇮🇱 · Marta Moscati🇩🇪 · Ulrich Nierste🇩🇪 · Ivan Nišandžić🇩🇪
The combined analysis of the BaBar, Belle, and LHCb data on $B \to D τ ν$ , $B \to D^{*} τ ν$ and $B_{c} \to J /Ψ τ ν$ decay observables shows evidence of physics beyond the Standard Model (SM). In this article, we study all the one- and two-dimensional scenarios which can be generated by adding a single new particle to the SM. We put special emphasis on the model-discriminating power of $F_{L} (D^{*})$ and of the $τ$ polarizations, and especially on the constraint from the branching fraction $BR (B_{c} \to τ ν)$ . We critically review this constraint and do not support the aggressive limit of $BR (B_{c} \to τ ν) < 10%$ used in some analyses. While the impact of $F_{L} (D^{*})$ is currently still limited, the $BR (B_{c} \to τ ν)$ constraint has a significant impact: depending on whether one uses a limit of $60%$ , $30%$ or $10%$ , the pull for new physics (NP) in scalar operators changes drastically. More specifically, for a conservative $60%$ limit a scenario with scalar operators gives the best fit to data, while for an aggressive $10%$ limit this scenario is strongly disfavored and the best fit is obtained in a scenario in which only a left-handed vector operator is generated. We find a sum rule for the branching ratios of $B \to D τ ν$ , $B \to D^{*} τ ν$ and $Λ_{b} \to Λ_{c} τ ν$ which holds for any NP contribution to the Wilson coefficients. This sum rule entails an enhancement of $BR (Λ_{b} \to Λ_{c} τ ν)$ over its SM prediction by $(24 \pm 6) %$ for the current $R (D^{(*)})$ data.
hep-phPRD(2019)·193 citations
09*
Probing the strange Higgs coupling at lepton colliders using light-jet flavor tagging
J. Duarte-Campderros🇪🇸 · G. Perez🇨🇭 · M. Schlaffer🇮🇱 · A. Soffer🇮🇱
We propose a method to probe the coupling of the Higgs to strange quarks by tagging strange jets at future lepton colliders. For this purpose we describe a jet-flavor observable, $J_{F}$ , that is correlated with the flavor of the quark associated with the hard part of the jet. Using this variable, we set up a strangeness tagger aimed at studying the decay $h \to s s ˉ$ . We determine the sensitivity of our method to the strange Yukawa coupling, and find it to be of the order of the standard-model expectation.
hep-phhep-exPRD(2020)·42 citations
10*
$U (1)$ flavour symmetries as Peccei-Quinn symmetries
Fredrik Björkeroth🇮🇹 · Luca Di Luzio🇮🇹 · Federico Mescia🇪🇸 · Enrico Nardi🇮🇹
We investigate to what extent a generic, generation-dependent $U (1)$ symmetry acting on the quark Yukawa operators can reduce the number of free parameters by forcing some entries in the Yukawa matrices to vanish. The maximal reduction compatible with CP violation yields nine real parameters and one phase, which matches the number of physical observables, implying that such models have no free parameters. We derive a set of results: (i) the only possible structures have the form $M_{4} \oplus M_{5}$ , where the subscripts indicate the number of real parameters in the Yukawa matrices, (ii) there are only two inequivalent Yukawa structures, each one giving rise to six different models depending on quark flavour assignments, (iii) the $U (1)$ symmetries that generate these textures all have a QCD anomaly, and hence are Peccei-Quinn symmetries, reinforcing the idea of a possible connection between the quark flavour puzzle and the axion solution to the strong CP problem, (iv) in some cases the contributions to the QCD anomaly of two generations cancels out, and this opens the possibility that the axion coupling to nucleons could be strongly suppressed. Flavour-violating axion couplings to quarks are completely fixed, up to the axion decay constant, providing a non-trivial complementarity between low-energy flavour-violating processes and standard axion searches.
hep-phJHEP(2019)·53 citations
11*
Hidden Inflaton Dark Matter
Juan P. Beltrán Almeida🇨🇴 · Nicolás Bernal🇨🇴 · Javier Rubio🇩🇪 · Tommi Tenkanen🇬🇧
If cosmic inflation was driven by an electrically neutral scalar field stable on cosmological time scales, the field necessarily constitutes all or part of dark matter (DM). We study this possibility in a scenario where the inflaton field $s$ resides in a hidden sector, which is coupled to the Standard Model sector through the Higgs portal $λ_{h s} s^{2} H^{†} H$ and non-minimally to gravity via $ξ_{s} s^{2} R$ . We study scenarios where the field $s$ first drives inflation, then reheats the Universe, and later constitutes all DM. We consider two benchmark scenarios where the DM abundance is generated either by production during reheating or via non-thermal freeze-in. In both cases, we take into account all production channels relevant for DM in the mass range from keV to PeV scale. On the inflationary side, we compare the dynamics and the relevant observables in two different but well-motivated theories of gravity (metric and Palatini), discuss multifield effects in case both fields ( $s$ and $h$ ) were dynamical during inflation, and take into account the non-perturbative nature of particle production during reheating. We find that, depending on the initial conditions for inflation, couplings and the DM mass, the scenario works well especially for large DM masses, $1 0^{2}$ GeV $≲ m_{s} ≲ 1 0^{6}$ GeV, although there are also small observationally allowed windows at the keV and MeV scales. We discuss how the model can be tested through astrophysical observations.
hep-phastro-ph.COJCAP(2019)·93 citations
12*
The four-propagator three-loop vacuum integral by the hypergeometry
Zhi-Hua Gu🇨🇳 · Hai-Bin Zhang🇨🇳
Hypergeometric function method is proposed to calculate the scalar integrals of Feynman diagrams. For the scalar integral of three-loop vacuum diagram with four-propagator, we verify the equivalency of Feynman parametrization and the hypergeometric technique. The result can be described as generalized hypergeometric functions of triple variables. Based on the triple hypergeometric functions, we also establish the systems of homogeneous linear partial differential equations(PDEs) satisfied by the mentioned scalar integral. The continuation of the scalar integral from its convergent regions to whole kinematic domains can be made numerically through the system of homogeneous linear PDEs with the help of the element method.
hep-phCPC(2019)·5 citations
13*
Hadron gas with repulsive mean field
Pasi Huovinen🇵🇱 · Peter Petreczky🇺🇸
We study the QCD equation of state, and fluctuations of baryon number and strangeness using the hadron resonance gas model with repulsive mean field. We find that including both the predicted but not observed resonances, a.k.a. missing states, and the repulsive mean field into the resonance gas model leads to better description of the lattice results. The repulsive mean field is particularly important for the higher order baryon number fluctuations.
↳ nucl-thhep-lathep-phPoS(2018)·1 citation
14*
Model Dependence of the Pion Form Factor Extracted from Pion Electro-production
Robert J. Perry🇦🇺 · Ayse Kızılersu🇦🇺 · Anthony W. Thomas🇦🇺
In 2008 the Jefferson Laboratory $F_{π}$ Collaboration released results for the pion electromagnetic form factor, which they extracted from pion electro-production data. The measured values for the pion form factor are model dependent, and require the use of the Vanderhaeghen, Guidal and Laget Regge Model for their extraction. While agreement between this model and data is impressive, the theoretical implementation of gauge invariance is less satisfying. We would like to establish how well the extracted form factor corresponds to the true form factor. To do this, we use a simple toy model, which imposes gauge invariance in a more theoretically satisfying way. The model form factor is extracted from our model cross section using the method employed by the $F_{π}$ Collaboration to extract the experimental pion form factor. We conclude that the reconstructed model form factor is a reasonable representation of the true model form factor for the kinematics chosen, although we note that the extracted form factor is smaller than the true form factor. This suggests that current extracted values of pion form factor may be overestimated.
↳ nucl-thhep-phPRC(2019)·10 citations
15*
Tau-lepton Physics at the FCC-ee circular e $^{+}$ e $^{-}$ Collider
Mogens Dam🇩🇰
The future FCC-ee collider is designed to deliver $e^{+} e^{-}$ collisions to study with ultimate precision the Z, W, and Higgs bosons, and the top quark. In a high-statistics scan around the Z pole, $1.3 \times 1 0^{11}$ events $Z \to τ τ$ will be produced, the largest sample of $τ τ$ events foreseen at any lepton collider. With their large boost, $τ$ leptons from Z decays are particularly well suited for precision measurements. The focus of this report is on tests of lepton universality from precision measurement of $τ$ properties and on tests of charged lepton flavour violation in Z decays and in $τ$ decays. In both of these areas, FCC-ee promises sensitivities well beyond present experimental limits.
↳ hep-exhep-phSciPost Phys.Proc.(2019)·81 citations
16*
Bound states in Functional Renormalization Group
A. Jakovac🇭🇺 · A. Patkos🇭🇺
Equivalence criteria are established for an effective Yukawa-type theory of composite fields representing two-particle fermion bound states with the original "microscopic" theory of interacting fermions based on the spectral decomposition of the 2-to-2 fermion scattering amplitude. Functional renormalisation group equations of the effective theory are derived exploiting relations expressing the equivalence. The effect of truncating the spectral decomposition is investigated quantitatively on the example of the non-relativistic bound states of two oppositely charged fermi particles.
↳ hep-thhep-phInt.J.Mod.Phys.A(2019)·14 citations
17*
Two-loop $N = 2$ SQCD amplitudes with external matter from iterated cuts
Gregor Kälin🇸🇪 · Gustav Mogull🇸🇪 · Alexander Ochirov🇨🇭
We develop an iterative method for constructing four-dimensional generalized unitarity cuts in $N = 2$ supersymmetric Yang-Mills (SYM) theory coupled to fundamental matter hypermultiplets ( $N = 2$ SQCD). For iterated two-particle cuts,specifically those involving only four-point amplitudes, this implies simple diagrammatic rules for assembling the cuts to any loop order, reminiscent of the rung rule in $N = 4$ SYM. By identifying physical poles, the construction simplifies the task of extracting complete integrands. In combination with the duality between color and kinematics we construct all four-point massless MHV-sector scattering amplitudes up to two loops in $N = 2$ SQCD, including those with matter on external legs. Our results reveal chiral infrared-finite integrands closely related to those found using loop-level BCFW recursion. The integrands are valid in $D \leq 6$ dimensions with external states in a four-dimensional subspace; the upper bound is dictated by our use of six-dimensional chiral $N = (1, 0)$ SYM as a means of dimensionally regulating loop integrals.
↳ hep-thhep-phJHEP(2019)·36 citations
18*
CEPC Conceptual Design Report: Volume 2 - Physics & Detector
The CEPC Study Group
The Circular Electron Positron Collider (CEPC) is a large international scientific facility proposed by the Chinese particle physics community to explore the Higgs boson and provide critical tests of the underlying fundamental physics principles of the Standard Model that might reveal new physics. The CEPC, to be hosted in China in a circular underground tunnel of approximately 100 km in circumference, is designed to operate as a Higgs factory producing electron-positron collisions with a center-of-mass energy of 240 GeV. The collider will also operate at around 91.2 GeV, as a Z factory, and at the WW production threshold (around 160 GeV). The CEPC will produce close to one trillion Z bosons, 100 million W bosons and over one million Higgs bosons. The vast amount of bottom quarks, charm quarks and tau-leptons produced in the decays of the Z bosons also makes the CEPC an effective B-factory and tau-charm factory. The CEPC will have two interaction points where two large detectors will be located. This document is the second volume of the CEPC Conceptual Design Report (CDR). It presents the physics case for the CEPC, describes conceptual designs of possible detectors and their technological options, highlights the expected detector and physics performance, and discusses future plans for detector R&D and physics investigations. The final CEPC detectors will be proposed and built by international collaborations but they are likely to be composed of the detector technologies included in the conceptual designs described in this document. A separate volume, Volume I, recently released, describes the design of the CEPC accelerator complex, its associated civil engineering, and strategic alternative scenarios.
↳ hep-exhep-ph1053 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.