HEP Phenomenology·hep-ph

Tue·Mar 26, 2019Tuesday·March 26, 2019

40 papers—29 primary·11 cross-listed·reconstructed*

01*
Vector-scalar mixing to all orders, for an arbitrary gauge model in the generic linear gauge
Adrian Lewandowski (Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern)🇨🇭
I give explicit fromulae for full propagators of vector and scalar fields in a generic spin-1 gauge model quantized in an arbitrary linear covariant gauge. The propagators, expressed in terms of all-order one-particle-irreducible correlation functions, have a remarkably simple form because of constraints originating from Slavnov-Taylor identities of Becchi-Rouet-Stora symmetry. I also determine the behavior of the propagators in the neighborhood of the poles, and give a simple prescription for the coefficients that generalize (to the case with an arbitrary vector-scalar mixing) the standard $Z$ factors of Lehmann, Symanzik and Zimmermann. So obtained generalized $Z$ factors, are indispensable to the correct extraction of physical amplitudes from the amputated correlation functions in the presence of mixing. The standard $R_{ξ}$ guauges form a particularly important subclass of gauges considered in this paper. While the tree-level vector-scalar mixing is, by construction, absent in $R_{ξ}$ gauges, it unavoidably reappears at higher orders. Therefore the prescription for the generalized $Z$ factors given in this paper is directly relevant for the extraction of amplitudes in $R_{ξ}$ gauges.
hep-phhep-thNPB(2019)·0 citations
02*
Violation of lepton number in 3 units
Renato M. Fonseca🇨🇿
The number of leptons may or may not be a conserved quantity. The Standard Model predicts that it is (in perturbative processes), but there is the well known possibility that new physics violates lepton number in one or two units. The first case ( $Δ L = 1$ ) is associated to proton decay into mesons plus a lepton or an anti-lepton, while the second one ( $Δ L = 2$ ) is usually associated to Majorana neutrino masses and neutrinoless double beta decay. It is also conceivable that leptons can only be created or destroyed in groups of three ( $Δ L = 3$ ). Colliders and proton decay experiments can explore this possibility.
hep-phJ.Phys.Conf.Ser.(2020)·1 citation
03*
Investigation of High Energy Behaviour of HERA Data
Agnieszka Luszczak🇵🇱 · Henri Kowalski🇩🇪
We analyse the high precision HERA $F_{2}$ data in the low- $x$ regions, $x < 0, 01$ and the very-low- $x$ , $x < 0.001$ , regions using $λ$ -Fits. $λ$ is a measure of the rate of rise of $F_{2}$ defined by $F_{2} \propto (1/ x)^{λ}$ . We show that $λ$ determined in these two regions, at various $Q^{2}$ values, is systematically smaller in the very-low- $x$ region as compared to the low- $x$ region. We discuss some possible physical interpretations of this effect.
hep-phPLB(2020)·2 citations
04*
Noncommutative approach to diagnose degenerate Higgs bosons at 125 GeV
M. A. De Andrade🇧🇷 · C. Neves🇧🇷
We propose a noncommutative (NC) version for a global O(2) scalar field theory, whose damping feature is introduced into the scalar field theory through the NC parameter. In this context, we investigate how noncommutative drives spontaneous symmetry breaking (SSB) and Higgs-Kibble mechanisms and how the damping feature workout. Indeed, we show that the noncommutativity plays an important role in such mechanisms, i.e., the Higgs mass and VEV dependent on NC parameter. After that, it is explored the consequences of noncommutativity dependence of Higgs mass and VEV: for the first, it is shown that there are a mass-degenerate Higgs bosons near 126.5 GeV, parametrized by the noncommutativity; for the second, the gauge fields gain masses that present a noncommutativity contribution.
hep-phhep-th1 citation
05*
Small-x analysis on the effect of gluon recombinations inside hadrons in light of the GLR-MQ-ZRS equation
M. Lalung🇮🇳 · P. Phukan🇮🇳 · J. K. Sarma🇮🇳
We present a study of the contribution of antishadowing effects on the gluon distribution functions $G (x, Q^{2})$ in light of the Gribov-Levin-Ryskin-Mueller-Qiu, Zhu-Ruan-Shen (GLR-MQ-ZRS) nonlinear equation at small- $x$ , where $x$ is the momentum fraction or Bjorken variable and $Q^{2}$ is the four momentum transfer squared or photon virtuality. In this work, we have solved the GLR-MQ-ZRS nonlinear equation using Regge like the behavior of gluons in the kinematic range of $1 0^{- 2} \leq x \leq 1 0^{- 6}$ and $5 G e V^{2} \leq Q^{2} \leq 100 G e V^{2}$ respectively. We have obtained the solution of $G (x, Q^{2})$ by considering two particular cases: (a) $α_{s}$ fixed; and (b) the leading order QCD dependency of $α_{s}$ on $Q^{2}$ . A comparative analysis is also performed where we compare the gluon distribution function due to inclusion of the antishadowing effect with that of the gluon distribution without including the antishadowing effect. Our obtained results of $G (x, Q^{2})$ are compared with NNPDF3.0, CT14 and PDF4LHC. We also compare our results with the result obtained from the IMParton C++ package. Using the solutions of $G (x, Q^{2})$ , we have also predicted $x$ and $Q^{2}$ evolution of the logarithmic derivative of proton's $F_{2}$ structure function i.e. $d F_{2} (x, Q^{2}) / d ln Q^{2}$ . We incorporated both the leading order(LO) and next-to-leading order (NLO) QCD contributions of the gluon-quark splitting kernels, in $d F_{2} (x, Q^{2}) / d ln Q^{2}$ . Our result of $d F_{2} (x, Q^{2}) / d ln Q^{2}$ agrees reasonably well with the experimental data recorded by HERA's H1 detector.
hep-phNPA(2019)·9 citations
06*
Non-quadratic improved Hessian PDF reweighting and application to CMS dijet measurements at 5.02 TeV
Kari J. Eskola🇫🇮 · Petja Paakkinen🇫🇮 · Hannu Paukkunen🇫🇮
Hessian PDF reweighting, or "profiling", has become a widely used way to study the impact of a new data set on parton distribution functions (PDFs) with Hessian error sets. The available implementations of this method have resorted to a perfectly quadratic approximation of the initial $χ^{2}$ function before inclusion of the new data. We demonstrate how one can take into account the first non-quadratic components of the original fit in the reweighting, provided that the necessary information is available. We then apply this method to the CMS measurement of dijet pseudorapidity spectra in proton-proton (pp) and proton-lead (pPb) collisions at 5.02 TeV. The measured pp dijet spectra disagree with next-to-leading order (NLO) theory calculations using the CT14 NLO PDFs, but upon reweighting the CT14 PDFs, these can be brought to a much better agreement. We show that the needed proton-PDF modifications also have a significant impact on the predictions for the pPb dijet distributions. Taking the ratio of the individual spectra, the proton-PDF uncertainties effectively cancel, giving a clean probe of the PDF nuclear modifications. We show that these data can be used to further constrain the EPPS16 nuclear PDFs and strongly support gluon nuclear shadowing at small $x$ and antishadowing at around $x \approx 0.1$ .
hep-phnucl-thEPJC(2019)·52 citations
07*
Searching for BSM neutrino interactions in dark matter detectors
Jonathan M. Link🇺🇸 · Xun-Jie Xu🇩🇪
Neutrino interactions beyond the Standard Model (BSM) are theoretically well motivated and have an important impact on the future precision measurement of neutrino oscillation. In this work, we study the sensitivity of a multi-ton-scale liquid Xenon dark matter detector equipped with an intense radiative neutrino source to various BSM neutrino-electron interactions. We consider the conventional Non-Standard Interactions (NSIs), other more generalized four-fermion interactions including scalar and tensor forms, and light-boson mediated interactions. The work shows that with realistic experimental setups, one can achieve unprecedented sensitivity to these BSM neutrino-electron interactions.
hep-phhep-exJHEP(2019)·34 citations
08*
The CP-symmetries of the 2HDM
Bohdan Grzadkowski🇵🇱 · Odd Magne Ogreid🇳🇴 · Per Osland🇳🇴
We discuss the three different classes of CP-symmetries that can be realized in a two-Higgs-doublet model, CP1, CP2 and CP3. We express conditions for realizing these symmetries in terms of masses and couplings of the model, thereby providing a way of verifying which, if any, of these symmetries is realized by nature.
hep-phJ.Phys.Conf.Ser.(2020)·2 citations
09*
QED challenges at FCC-ee precision measurements
S. Jadach🇵🇱 · M. Skrzypek🇵🇱
The expected experimental precision of the rates and asymmetries in the Future Circular Collider with electron positron beams (FCC-ee) in the centre of the mass energy range 88-365GeV considered for construction in CERN, will be better by a factor 5-200. This will be thanks to very high luminosity, factor up to $1 0^{5}$ higher than in the past LEP experiments. This poses the extraordinary challenge of improving the precision of the Standard Model predictions by a comparable factor. In particular the perturbative calculations of the trivial QED effects, which have to be removed from the experimental data, are considered to be a major challenge for almost all quantities to be measured at FCC-ee. The task of this paper is to summarize on the "state of the art" in this class of the calculations left from the LEP era and to examine what is to be done to match the precision of the FCC-ee experiments -- what kind of technical advancements are necessary. The above analysis will be done for most important observables of the FCC-ee like the total cross sections near $Z$ and $W W$ threshold, charge asymmetries, the invisible width of $Z$ boson, the spin asymmetry from $τ$ lepton decay and the luminosity measurement.
hep-phEPJC(2019)·31 citations
10*
Nucleosynthesis in heavy-ion collisions at the LHC via the Saha equation
Volodymyr Vovchenko🇩🇪 · Kai Gallmeister🇩🇪 · Jürgen Schaffner-Bielich🇩🇪 · Carsten Greiner🇩🇪
The production of light (anti-)(hyper-)nuclei in heavy-ion collisions at the LHC is considered in the framework of the Saha equation, making use of the analogy between the evolution of the early universe after the Big Bang and that of "Little Bangs" created in the lab. Assuming that disintegration and regeneration reactions involving light nuclei proceed in relative chemical equilibrium after the chemical freeze-out of hadrons, their abundances are determined through the famous cosmological Saha equation of primordial nucleosynthesis and show no exponential dependence on the temperature typical for the thermal model. A quantitative analysis, performed using the hadron resonance gas model in partial chemical equilibrium, shows agreement with experimental data of the ALICE collaboration on d, $^{3}$ He, $_{Λ}^{3}$ H, and $^{4}$ He yields for a very broad range of temperatures at $T ≲ 155$ MeV. The presented picture is supported by the observed suppression of resonance yields in central Pb-Pb collisions at the LHC.
hep-phnucl-exnucl-thPLB(2020)·50 citations
11*
Probing the linear polarization of photons in ultraperipheral heavy ion collisions
Cong Li🇨🇳 · Jian Zhou🇨🇳 · Ya-jin Zhou🇨🇳
We propose to measure the linear polarization of the external electromagnetic fields of a relativistic heavy ion through azimuthal asymmetries in dilepton production in ultraperipheral collisions. The asymmetries estimated with the equivalent photon approximation are shown to be sizable.
hep-phPLB(2019)·96 citations
12*
The $B$ Anomalies and New Physics in $b \to s e^{+} e^{-}$
Alakabha Datta🇺🇸 · Jacky Kumar🇨🇦 · David London🇨🇦
We investigate the implications of the latest LHCb measurement of $R_{K}$ for NP explanations of the $B$ anomalies. The previous data could be explained if the $b \to s μ^{+} μ^{-}$ NP is in (I) $C_{9, NP}^{μμ}$ or (II) $C_{9, NP}^{μμ} = - C_{10, NP}^{μμ}$ , with scenario (I) providing a better explanation than scenario (II). This continues to hold with the new measurement of $R_{K}$ . However, for both scenarios, this measurement leads to a slight tension of $O (1 σ)$ between separate fits to the $b \to s μ^{+} μ^{-}$ and $R_{K^{(*)}}$ data. In this paper, we investigate whether this tension can be alleviated with the addition of NP in $b \to s e^{+} e^{-}$ . In particular, we examine the effect of adding such NP to scenarios (I) and (II). We find several scenarios in which this leads to improvements in the fits. $Z^{'}$ and LQ models with contributions to both $b \to s μ^{+} μ^{-}$ and $b \to s e^{+} e^{-}$ can reproduce the data, but only within scenarios based on (II). If the tension persists in future measurements, it may be necessary to consider NP models with more than one particle contributing to $b \to s ℓ^{+} ℓ^{-}$ .
hep-phPLB(2019)·134 citations
13*
Revisiting Quantum Stabilization of the Radion in Randall-Sundrum Model
Naoyuki Haba🇯🇵 · Toshifumi Yamada🇯🇵
We study the stabilization of the radion in Randall-Sundrum-1 model by the Casimir energy of a bulk gauge field. The Casimir energy is proportional to a divergent, infinite summation over the zeros of a Wronskian of Bessel functions that implicitly depends on the radion vacuum expectation value, and its regularization and renormalization is the central issue. We carry out the correct regularization and renormalization by noting that analytic continuation must be performed only on functions that are independent of the radion vacuum expectation value. Thereby we find that the 1-loop effective potential of the radion generated by the Casimir energy can be renormalized with the boundary tensions, and we correctly obtain the renormalized effective potential. It is shown that a bulk gauge field satisfying Dirichlet condition at the positive (UV) boundary and Dirichlet condition at the negative (IR) boundary gives rise to an appropriate radion potential that stabilizes the radion vacuum expectation value in a way that a large hierarchy of the warp factor is generated naturally.
hep-ph5 citations
14*
On explaining the observed pattern of quark and lepton masses
Jiri Hosek🇨🇿
Higgs sector of the Standard model (SM) is replaced by the gauge $S U (3)_{f}$ quantum flavor dynamics (QFD) with one parameter, the scale $Λ$ . Anomaly freedom of QFD demands extension of the fermion sector of SM by three sterile right-handed neutrino fields. Poles of fermion propagators with chirality-changing self-energies $Σ (p^{2})$ spontaneously generated by QFD at strong coupling define: (1) Three sterile-neutrino Majorana masses $M_{f R}$ of order $Λ$ . (2) Three Dirac masses $m_{f}$ , degenerate for $e_{f}, ν_{f}, u_{f}, d_{f}$ in family $f$ , exponentially small with respect to $Λ$ . Goldstone theorem implies: All eight flavor gluons acquire masses of order $M_{f R}$ . $W$ and $Z$ bosons acquire masses of order $\sum m_{f}$ , the effective Fermi scale. Composite 'would-be' Nambu-Goldstone bosons have their 'genuine' partners, the composite Higgs particles: The SM-like Higgs $h$ and two new Higgses $h_{3}$ and $h_{8}$ , all with masses at Fermi scale; three Higgses $χ_{i}$ with masses at scale $Λ$ . Large pole-mass splitting of charged leptons and quarks in $f$ is arguably due to full QED $Σ (p^{2})$ -dependent fermion-photon vertices enforced by Ward-Takahashi identities. The argument relies on illustrative computation of pole-mass splitting found non-analytic in fermion electric charges. Neutrinos are the Majorana particles with seesaw mass spectrum computed solely by QFD. Available data fix $Λ$ to, say, $Λ \sim 1 0^{14} GeV$ .
hep-ph0 citations
15*
Standard Model radiative corrections in the pion form factor measurements do not explain the $a_{μ}$ anomaly
Francisco Campanario🇪🇸 · Henryk Czyż🇵🇱 · Janusz Gluza🇵🇱 · Tomasz Jeliński🇵🇱 · Germán Rodrigo🇪🇸 · Szymon Tracz🇵🇱 · Dmitry Zhuridov🇵🇱
In this letter, we address the question of whether the almost four standard deviations difference between theory and experiment for the muon anomalous magnetic moment $a_{μ}$ can be explained as a higher-order Standard Model perturbation effect in the pion form factor measurements. This question has, until now, remained open, obscuring the source of discrepancies between the measurements. We calculate the last radiative corrections for the extraction of the pion form factor, which were believed to be potentially substantial enough to explain the data within the Standard Model. We find that the corrections are too small to diminish existing discrepancies in the determination of the pion form factor for different kinematical configurations of low-energy BABAR, BESS-III and KLOE experiments. Consequently, they cannot noticeably change the previous predictions for $a_{μ}$ and decrease the deviations between theory and direct measurements. To solve the above issues, new data and better understanding of low-energy experimental setups are needed, especially as new direct $a_{μ}$ measurements at Fermilab and J-PARC will provide new insights and substantially shrink the experimental error.
hep-phPRD(2019)·89 citations
16*
The Hydrogen Bond of QCD
L. Maiani🇮🇹 · A. D. Polosa🇮🇹 · V. Riquer🇮🇹
Using the Born-Oppenheimer approximation, we show that exotic resonances, X and Z, may emerge as QCD molecular objects made of colored two-quark lumps, states with heavy-light diquarks spatially separated from antidiquarks. With the same method we confirm that doubly heavy tetraquarks are stable against strong decays. Tetraquarks described here provide a new picture of exotic hadrons, as formed by the QCD analog of the hydrogen bond of molecular physics.
hep-phPRD(2019)·33 citations
17*
Looking for $B \to X_{s} ℓ^{+} ℓ^{-}$ in non-minimal Universal Extra Dimensional model
Avirup Shaw🇮🇳
Non-vanishing boundary localised terms significantly modify the mass spectrum and various interactions among the Kaluza-Klein excited states of 5-Dimensional Universal Extra Dimensional scenario. In this scenario we compute the contributions of Kaluza-Klein excitations of gauge bosons and third generation quarks for the decay process $B \to X_{s} ℓ^{+} ℓ^{-}$ incorporating next-to-leading order QCD corrections. We estimate branching ratio as well as Forward Backward asymmetry associated with this decay process. Considering the constraints from some other $b \to s$ observables and electroweak precision data we show that significant amount of parameter space of this scenario has been able to explain the observed experimental data for this decay process. From our analysis we put lower limit on the size of the extra dimension by comparing our theoretical prediction for branching ratio with the corresponding experimental data. Depending on the values of free parameters of the present scenario, lower limit on the inverse of the radius of compactification ( $R^{- 1}$ ) can be as high as $\geq 760$ GeV. {Even this value could slightly be higher if we project the upcoming measurement by Belle II experiment.} Unfortunately, the Forward Backward asymmetry of this decay process would not provide any significant limit on $R^{- 1}$ in the present model.
hep-phPRD(2019)·10 citations
18*
Theta dependence of the vacuum energy density in chiral effective Lagrangian models at finite temperature, above $T_{c}$
Enrico Meggiolaro🇮🇹
In this work, extending a previous study at zero temperature ( $T = 0$ ), we perform a systematic study of the modifications to the QCD vacuum energy density $ϵ_{v a c}$ in the finite-temperature case, above the chiral transition at $T_{c}$ , caused by a nonzero value of the parameter $θ$ , using two different effective Lagrangian models which implement the $U (1)$ axial anomaly of the fundamental theory and which are both well defined also above $T_{c}$ . In particular, we derive (and critically compare) the expressions for the topological susceptibility $χ$ and for the second cumulant $c_{4}$ starting from the $θ$ dependence of $ϵ_{v a c} (θ)$ in the two models.
hep-phhep-lathep-thPRD(2019)·5 citations
19*
Identifying the $Ξ_{b} (6227)$ and $Σ_{b} (6097)$ as $P$ -wave bottom baryons of $J^{P} = 3/ 2^{-}$
Er-Liang Cui🇨🇳 · Hui-Min Yang🇨🇳 · Hua-Xing Chen🇨🇳 · Atsushi Hosaka🇯🇵
We use the method of QCD sum rules within the framework of heavy quark effective theory to study the mass spectrum of the $Σ_{b} (6097)^{\pm}$ and $Ξ_{b} (6227)^{-}$ , and use the method of light-cone sum rules still within the heavy quark effective theory to study their decay properties. Our results suggest that they can be well interpreted as $P$ -wave bottom baryons with the spin-parity $J^{P} = 3/ 2^{-}$ . They belong to the baryon doublet $[6_{F}, 2, 1, λ]$ , where the total and spin angular momenta of the light degree of freedom are $j_{l} = 2$ and $s_{l} = 1$ , and the orbital angular momentum is between the bottom quark and the two-light-quark system ( $λ$ -type). This doublet contains six bottom baryons, and we predict masses (mass differences) and decay widths of the other four states to be $M_{Ω_{b} (3/ 2^{-})} = 6.46 \pm 0.12 GeV$ , $Γ_{Ω_{b} (3/ 2^{-})} = 58_{- 33}^{+ 65} MeV$ , $M_{Σ_{b} (5/ 2^{-})} - M_{Σ_{b} (3/ 2^{-})} = 13 \pm 5 MeV$ , $M_{Ξ_{b}^{'} (5/ 2^{-})} - M_{Ξ_{b}^{'} (3/ 2^{-})} = 12 \pm 5 MeV$ , and $M_{Ω_{b} (5/ 2^{-})} - M_{Ω_{b} (3/ 2^{-})} = 11 \pm 5 MeV$ . We propose to search for them in further LHCb experiments.
hep-phhep-exPRD(2019)·46 citations
20*
B-decay discrepancies after Moriond 2019
Jason Aebischer🇩🇪 · Wolfgang Altmannshofer🇺🇸 · Diego Guadagnoli🇫🇷 · Meril Reboud🇫🇷 · Peter Stangl🇫🇷 · David M. Straub🇩🇪
Following the updated measurement of the lepton flavour universality (LFU) ratio R_K in B -> Kll decays by LHCb, as well as a number of further measurements, e.g. R_K* by Belle and B_s -> mu mu by ATLAS, we analyse the global status of new physics in b -> s transitions in the weak effective theory at the b-quark scale, in the Standard Model effective theory at the electroweak scale, and in simplified models of new physics. We find that the data continues to strongly prefer a solution with new physics in semi-leptonic Wilson coefficients. A purely muonic contribution to the combination C_9 = -C_10, well suited to UV-complete interpretations, is now favoured with respect to a muonic contribution to C_9 only. An even better fit is obtained by allowing an additional LFU shift in C_9. Such a shift can be renormalization-group induced from four-fermion operators above the electroweak scale, in particular from semi-tauonic operators, able to account for the potential discrepancies in b -> c transitions. This scenario is naturally realized in the simplified U_1 leptoquark model. We also analyse simplified models where a LFU effect in b -> sll is induced radiatively from four-quark operators and show that such a setup is on the brink of exclusion by LHC di-jet resonance searches.
hep-phhep-exEPJC(2020)·329 citations
21*
$b \to s ℓ^{+} ℓ^{-}$ Transitions in Two-Higgs-Doublet Models
Andreas Crivellin🇨🇭 · Dario Müller🇨🇭 · Christoph Wiegand🇨🇭
In this article we study $b \to s μ^{+} μ^{-}$ transitions and possible correlations with the anomalous magnetic moment of the muon ( $a_{μ}$ ) within two-Higgs-doublet models with generic Yukawa couplings, including the possibility of right-handed neutrinos. We perform the matching on the relevant effective Hamiltonian and calculate the leading one-loop effects for $b \to s ℓ ℓ^{(')}$ , $b \to s γ$ , $Δ B = Δ S = 2$ , $b \to s ν ν ˉ$ and $ℓ \to ℓ^{'} γ$ transitions in a general $R_{ξ}$ gauge. Concerning the phenomenology, we find that an explanation of the hints for new physics in $b \to s μ^{+} μ^{-}$ data is possible once right-handed neutrinos are included. If lepton flavour violating couplings are allowed, one can account for the discrepancy in $a_{μ}$ as well. However, only a small portion of parameter space gives a good fit to $b \to s μ^{+} μ^{-}$ data and the current bound on $h \to τ μ$ requires the mixing between the neutral Higgses to be very small if one aims at an explanation of $a_{μ}$ .
hep-phhep-exJHEP(2019)·98 citations
22*
Solutions to $R_{D}$ - $R_{D^{*}}$ in light of Belle 2019 data
Ashutosh Kumar Alok🇮🇳 · Dinesh Kumar🇵🇱 · Suman Kumbhakar🇮🇳 · S Uma Sankar🇮🇳
Earlier this year, the Belle collaboration presented their new measurements of $R_{D}$ and $R_{D^{*}}$ using a new method. These measurements are consistent with the Standard Model predictions, whereas the global averages of the earlier measurements had a $4.1 σ$ discrepancy. With the inclusion of the new data in the global averages, the discrepancy comes down to $3.1 σ$ . In this work, we study the study the new physics solutions to the $R_{D}$ - $R_{D^{*}}$ anomaly allowed by the reduction in the discrepancy. Among the four fermion operators, which arise through a single particle exchange, only the $(V - A)$ operator solution survives. We found three additional solutions with two dis-similar operators. The branching ratio of $B_{c} \to τ ν ˉ$ is powerful discriminant between these four allowed solutions.
hep-phNPB(2020)·53 citations
23*
$Δ A_{C P}$ within the Standard Model and beyond
Mikael Chala🇬🇧 · Alexander Lenz🇬🇧 · Aleksey V. Rusov🇬🇧 · Jakub Scholtz🇬🇧
In light of the recent LHCb observation of CP violation in the charm sector, we review standard model (SM) predictions in the charm sector and in particular for $Δ A_{C P}$ . We get as an upper bound in the SM $∣Δ A_{C P}^{SM} ∣ \leq 3.6 \times 1 0^{- 4}$ , which can be compared to the measurement of $Δ A_{C P}^{LHCb2019} = (- 15.4 \pm 2.9) \times 1 0^{- 4}$ . We discuss resolving this tension within an extension of the SM that includes a flavour violating $Z^{'}$ that couples only to $s ˉ s$ and $c ˉ u$ . We show that for masses below 80 GeV and flavour violating coupling of the order of $1 0^{- 4}$ , this model can successfully resolve the tension and avoid constraints from dijet searches, $D^{0} - D^{0}$ mixing and measurements of the $Z$ width.
hep-phhep-exJHEP(2019)·104 citations
24*
Hunting On- and Off-Axis for Light Dark Matter with DUNE-PRISM
Valentina De Romeri🇪🇸 · Kevin J. Kelly🇺🇸 · Pedro A.N. Machado🇺🇸
We explore the sensitivity of the Deep Underground Neutrino Experiment (DUNE) near detector and the proposed DUNE-PRISM movable near detector to sub-GeV dark matter, specifically scalar dark matter coupled to the Standard Model via a sub-GeV dark photon. We consider dark matter produced in the DUNE target that travels to the detector and scatters off electrons. By combining searches for dark matter at many off-axis positions with DUNE-PRISM, sensitivity to this scenario can be much stronger than when performing a measurement at one on-axis position.
hep-phhep-exPRD(2019)·83 citations
25*
Effective alignments and the landscape of $S_{4}$ flavour models
Ivo de Medeiros Varzielas🇵🇹 · Miguel Levy🇵🇹 · Ye-Ling Zhou🇬🇧
We explore the concept of effective alignments: contractions of multiple flavour symmetry breaking flavon fields. These contractions give rise to directions that are hard or impossible to obtain directly by breaking the flavour symmetry. Within this context, and using $S_{4}$ as the flavour symmetry to exemplify, we perform a phenomenological check of lepton flavour models built from pairing any two effective alignments up to order 2 (in flavon contractions). The check is performed for each pair of effective alignments in a framework with models of constrained sequential dominance type, in a basis where the charged leptons are diagonal. We thus obtain an indication of which effective alignments are interesting for model building, within this so-called $S_{4}$ landscape. We find three types of viable topologies and provide examples of models realizing this strategy for each topology.
hep-phPRD(2019)·13 citations
26*
Two-component Dark Matter with co-genesis of Baryon Asymmetry of the Universe
Debasish Borah🇮🇳 · Arnab Dasgupta🇰🇷 · Sin Kyu Kang🇰🇷
We discuss the possibility of realising a two-component dark matter (DM) scenario where the two DM candidates differ from each other by virtue of their production mechanism in the early universe. One of the DM candidates is thermally generated in a way similar to the weakly interacting massive particle (WIMP) paradigm where the DM abundance is governed by its freeze-out while the other candidate is produced only from non-thermal contributions similar to freeze-in mechanism. We discuss this in a minimal extension of the standard model where light neutrino masses arise radiatively in a way similar to the scotogenic models with DM particles going inside the loop. The lepton asymmetry is generated at the same time from WIMP DM annihilations as well as partially from the mother particle for non-thermal DM. This can be achieved while satisfying the relevant experimental bounds, and keeping the scale of leptogenesis or the thermal DM mass as low as 3 TeV, well within present experimental reach. In contrast to the TeV scale thermal DM mass, the non-thermal DM can be as low as a few keV, giving rise to the possibility of a sub-dominant warm dark matter (WDM) component that can have interesting consequences on structure formation. The model also has tantalizing prospects of being detected at ongoing direct detection experiments as well as the ones looking for charged lepton flavour violating process like $μ \to e γ$ .
hep-phastro-ph.COPRD(2019)·31 citations
27*
NNLO corrections to false vacuum decay rate in thin-wall approximation
M.A. Bezuglov🇷🇺 · A.I. Onishchenko🇷🇺
Recently it was discovered that the Standard Model vacuum may suffer an essential metastability near the Planck scale. In this regard it makes sense to study in more detail the decay processes of the metastable vacuum and to develop methods for their more accurate analysis. In this article we develop a technique to calculate two loop radiative corrections to false vacuum decay rate in thin-wall approximation and apply it to false vacuum decay in scalar quantum field theory with cubic and quartic interactions. The results obtained use dimensional regularization and given in two different renormalization schemes: Coleman-Weinberg and $M S$ .
hep-phhep-thquant-ph3 citations
28*
Analysis of the hidden-bottom tetraquark mass spectrum with the QCD sum rules
Zhi-Gang Wang🇨🇳
In this article, we extend our previous work to study the mass spectrum of the ground state hidden-bottom tetraquark states with the QCD sum rules in a systematic way. The predicted hidden-bottom tetraquark masses can be confronted to the experimental data in the future to diagnose the nature of the $Z_{b}$ states. In calculations, we observe that the scalar diquark states, the axialvector diquark states and the axialvector components of the tensor diquark state are all good diquarks in building the lowest tetraquark states.
hep-phEPJC(2019)·34 citations
29*
Prospects for Searching Thermal Effects, Non-Newtonian Gravity and Axion-Like Particles: Cannex Test of the Quantum Vacuum
Galina L. Klimchitskaya🇷🇺 · Vladimir M. Mostepanenko🇷🇺 · René I. P. Sedmik🇦🇹 · Hartmut Abele🇦🇹
We consider the CANNEX (Casimir And Non-Newtonian force EXperiment) test of the quantum vacuum intended for measuring the gradient of the Casimir pressure between two flat parallel plates at large separations and constraining parameters of the chameleon model of dark energy in cosmology. A modification of the measurement scheme is proposed that allows simultaneous measurements of both the Casimir pressure and its gradient in one experiment. It is shown that with several improvements the CANNEX test will be capable to strengthen the constraints on the parameters of the Yukawa-type interaction by up to an order of magnitude over a wide interaction range. The constraints on the coupling constants between nucleons and axion-like particles, which are considered as the most probable constituents of dark matter, could also be strengthened over a region of axion masses from 1 to 100 meV.
hep-phastro-ph.COhep-thquant-phSymmetry(2019)·26 citations
30*
Large- $N_{c}$ and Large- $N_{F}$ Limits of SU( $N_{c}$ ) Gauge Theories with Fermions in Different Representations
Sudhakantha Girmohanta🇺🇸 · Thomas A. Ryttov🇩🇰 · Robert Shrock🇺🇸
We present calculations of certain limits of scheme-independent series expansions for the anomalous dimensions of gauge-invariant fermion bilinear operators and for the derivative of the beta function at an infrared fixed point in SU( $N_{c}$ ) gauge theories with fermions transforming according to two different representations. We first study a theory with $N_{f}$ fermions in the fundamental representation and $N_{f^{'}}$ fermions in the adjoint or symmetric or antisymmetric rank-2 tensor representation, in the limit $N_{c} \to \infty$ , $N_{f} \to \infty$ with $N_{f} / N_{c}$ fixed and finite. We then study the $N_{c} \to \infty$ limit of a theory with fermions in the adjoint and rank-2 symmetric or antisymmetric tensor representations.
↳ hep-thhep-lathep-phPRD(2019)·6 citations
31*
Chiral-Imbalance Density Wave in Baryonic Matters
Mamiya Kawaguchi🇯🇵 · Shinya Matsuzaki🇨🇳
We propose a new chirality-imbalance phenomenon arising in baryonic/high dense matters under a magnetic field. A locally chiral-imbalanced (parity-odd) domain can be created due to the electromagnetically induced $U (1)_{A}$ anomaly in high-dense matters. The proposed local-chiral imbalance generically possesses a close relationship to a spacial distribution of an inhomogeneous chiral (pion)-vector current coupled to the magnetic field. To demonstrate such a nontrivial correlation, we take the skyrmion crystal approach to model baryonic/high dense matters. Remarkably enough, we find the chirality-imbalance distribution takes a wave form in a high density region (dobbed ``chiral-imbalance density wave''), when the inhomogeneous chiral condensate develops to form a chiral density wave. This implies the emergence of a nontrivial density wave for the explicitly broken $U (1)_{A}$ current simultaneously with the chiral density wave for the spontaneously broken chiral-flavor current. We further find that the topological phase transition in the skyrmion crystal model (between skyrmion and half-skyrmion phases) undergoes the deformation of the chiral-imbalance density wave in shape and periodicity. The emergence of this chiral-imbalance density wave could give a crucial contribution to studies on the chiral phase transition, as well as the nuclear matter structure, in compact stars under a magnetic field.
↳ nucl-thhep-phJ.Phys.G(2020)·1 citation
32*
Principal Component Analysis of collective flow in Relativistic Heavy-Ion Collisions
Ziming Liu🇨🇳 · Wenbin Zhao🇨🇳 · Huichao Song (Peking U.)🇨🇳
In this paper, we implement Principal Component Analysis (PCA) to study the single particle distributions generated from thousands of {\tt VISH2+1} hydrodynamic simulations with an aim to explore if a machine could directly discover flow from the huge amount of data without explicit instructions from human-beings. We found that the obtained PCA eigenvectors are similar to but not identical with the traditional Fourier bases. Correspondingly, the PCA defined flow harmonics $v_{n}^{'}$ are also similar to the traditional $v_{n}$ for $n = 2$ and 3, but largely deviated from the Fourier ones for $n \geq 4$ . A further study on the symmetric cumulants and the Pearson coefficients indicates that mode-coupling effects are reduced for these flow harmonics defined by PCA.
↳ nucl-thcond-mat.dis-nnhep-phnucl-exEPJC(2019)·36 citations
33*
Scratches from the Past: Inflationary Archaeology through Features in the Power Spectrum of Primordial Fluctuations
Anže Slosar · Xingang Chen · Cora Dvorkin · Daniel Green · P. Daniel Meerburg · Eva Silverstein · Benjamin Wallisch (for 144 endorsers)
Inflation may provide unique insight into the physics at the highest available energy scales that cannot be replicated in any realistic terrestrial experiment. Features in the primordial power spectrum are generically predicted in a wide class of models of inflation and its alternatives, and are observationally one of the most overlooked channels for finding evidence for non-minimal inflationary models. Constraints from observations of the cosmic microwave background cover the widest range of feature frequencies, but the most sensitive constraints will come from future large-scale structure surveys that can measure the largest number of linear and quasi-linear modes.
↳ astro-ph.COhep-phhep-thBull.Am.Astron.Soc.(2019)·118 citations
34*
Memory effect in Yang-Mills theory
Niko Jokela🇫🇮 · K. Kajantie🇫🇮 · Miika Sarkkinen🇫🇮
We study the empirical realisation of the memory effect in Yang-Mills theory, especially in view of the classical vs. quantum nature of the theory. Gauge invariant analysis of memory in classical U(1) electrodynamics and its observation by total change of transverse momentum of a charge is reviewed. Gauge fixing leads to a determination of a gauge transformation at infinity. An example of Yang-Mills memory then is obtained by reinterpreting known results on interactions of a quark and a large high energy nucleus in the theory of Color Glass Condensate. The memory signal is again a kick in transverse momentum, but it is only obtained in quantum theory after fixing the gauge, after summing over an ensemble of classical processes.
↳ hep-thgr-qchep-phPRD(2019)·19 citations
35*
Exploring the partonic phase at finite chemical potential within an extended off-shell transport approach
Pierre Moreau🇩🇪 · Olga Soloveva🇩🇪 · Lucia Oliva🇩🇪 · Taesoo Song🇩🇪 · Wolfgang Cassing🇩🇪 · Elena Bratkovskaya🇩🇪
We extend the Parton-Hadron-String Dynamics (PHSD) transport approach in the partonic sector by explicitly calculating the total and differential partonic scattering cross sections as a function of temperature $T$ and baryon chemical potential $μ_{B}$ on the basis of the effective propagators and couplings from the Dynamical QuasiParticle Model (DQPM) that is matched to reproduce the equation of state of the partonic system above the deconfinement temperature $T_{c}$ from lattice QCD. The ratio of shear viscosity $η$ over entropy density $s$ , i.e. $η / s$ , is evaluated using the collisional widths and compared to lQCD calculations for $μ_{B}$ = 0 as well. We find only a very modest change of $η / s$ with the baryon chemical $μ_{B}$ . This also holds for a variety of hadronic observables from central A+A and C+Au collisions in the energy range 5 GeV $\leq s_{N N} \leq$ 200 GeV when implementing the differential cross sections into the PHSD approach. We only observe small differences in the strangeness and antibaryon sector with practically no sensitivity of rapidity and $p_{T}$ distributions to the $μ_{B}$ dependence of the partonic cross sections. Since we find only small traces of a $μ_{B}$ -dependence in heavy-ion observables - although the effective partonic masses and widths as well as their partonic cross sections clearly depend on $μ_{B}$ - this implies that one needs a sizable partonic density and large space-time QGP volume to explore the dynamics in the partonic phase. These conditions are only fulfilled at high bombarding energies where $μ_{B}$ is, however, rather low. On the other hand, when decreasing the bombarding energy and thus increasing $μ_{B}$ , the hadronic phase becomes dominant and accordingly, it will be difficult to extract signals from the partonic dynamics based on "bulk" observables.
↳ nucl-thhep-phPRC(2019)·100 citations
36*
Relativistic self-energy decomposition of nuclear symmetry energy and equation of state of neutron matter within QCD sum rules
Bao-Jun Cai🇨🇳 · Lie-Wen Chen🇨🇳
Abstract (abridged edition): Properties of the relativistic nucleon self-energy decomposition of the symmetry energy as well as the equation of state (EOS) of pure neutron matter (PNM) are explored systematically within the QCD sum rules (QCDSR). Our results in the present work have demonstrated that the QCDSR approach can be used to explore the properties of asymmetric nuclear matter (ANM) in a quantitative manner, at least in lower density region. The QCDSR approach establishes a bridge connecting the EOS of ANM and the non-perturbative QCD vacuum, and thus provides a useful way to understand the properties of dense nucleonic matter from non-perturbative QCD vacuum. These studies are helpful to investigate the QCD origins about the uncertainties of nucleonic matter properties, e.g., the uncertainties of the symmetry energy. On the other hand, the exact knowledge on the EOS of ANM extracted from experiments, observations and model-independent calculations is also very useful for understanding the quark/gluon condensates in nuclear medium, which can provide important information on the chiral symmetry restoration phase transition in nuclear matter as well as the in-medium effects of hadron properties.
↳ nucl-thhep-phnucl-exPRC(2019)·12 citations
37*
Frequency-splitting estimators of single-propagator traces
Leonardo Giusti🇮🇹 · Tim Harris🇮🇹 · Alessandro Nada🇩🇪 · Stefan Schaefer🇩🇪
Single-propagator traces are the most elementary fermion Wick contractions which occur in numerical lattice QCD, and are usually computed by introducing random-noise estimators to profit from volume averaging. The additional contribution to the variance induced by the random noise is typically orders of magnitude larger than the one due to the gauge field. We propose a new family of stochastic estimators of single-propagator traces built upon a frequency splitting combined with a hopping expansion of the quark propagator, and test their efficiency in two-flavour QCD with pions as light as 190 MeV. Depending on the fermion bilinear considered, the cost of computing these diagrams is reduced by one to two orders of magnitude or more with respect to standard random-noise estimators. As two concrete examples of physics applications, we compute the disconnected contributions to correlation functions of two vector currents in the isosinglet omega channel and to the hadronic vacuum polarization relevant for the muon anomalous magnetic moment. In both cases, estimators with variances dominated by the gauge noise are computed with a modest numerical effort. Theory suggests large gains for disconnected three and higher point correlation functions as well. The frequency-splitting estimators and their split-even components are directly applicable to the newly proposed multi-level integration in the presence of fermions.
↳ hep-lathep-phEPJC(2019)·72 citations
38*
Spontaneous scalarization of boson stars
Yves Brihaye (Uni Mons, Belgium)🇧🇪 · Betti Hartmann (IFSC, Universidade de São Paulo, Brazil)🇧🇷
We study the spontaneous scalarization of spherically symmetric, asymptotically flat boson stars in the $(α R + γ G) ϕ^{2}$ scalar-tensor gravity model. These compact objects are made of a complex valued scalar field that has harmonic time dependence, while their space-time is static and they can reach densities and masses similar to that of supermassive black holes. We find that boson stars can be scalarized for both signs of the scalar-tensor coupling $α$ and $γ$ , respectively. This is, in particular, true for boson stars that are {\it a priori} stable with respect to decay into individual bosonic particles. A fundamental difference between the $α$ - and $γ$ -scalarization exists, though: while we find an interval in $α > 0$ for which boson stars can {\it never} be scalarized when $γ = 0$ , there is no restriction on $γ \neq = 0$ when $α = 0$ . Typically, two branches of solutions exist that differ in the way the boson star gets scalarized: either the scalar field is maximal at the center of the star, or on a shell with finite radius which roughly corresponds to the outer radius of the boson star. We also demonstrate that the former solutions can be radially excited.
↳ gr-qchep-phhep-thJHEP(2019)·20 citations
39*
Extracting the Top-Quark Width from Non-Resonant Production
Christian Herwig🇺🇸 · Tomáš Ježo🇨🇭 · Benjamin Nachman🇺🇸
In the context of the Standard Model (SM) of particle physics, the relationship between the top-quark mass and width ( $Γ_{t}$ ) has been precisely calculated. However, the uncertainty from current direct measurements of the width is nearly 50%. A new approach for directly measuring the top-quark width using events away from the resonance peak is presented. By using an orthogonal dataset to traditional top-quark width extractions, this new method may enable significant improvements in the experimental sensitivity in a method combination. Recasting a recent ATLAS differential cross section measurement, we find $Γ_{t}$ = 1.28 $\pm$ 0.30 GeV (1.33 $\pm$ 0.29 GeV expected), providing the most precise direct measurement of the width.
↳ hep-exhep-phPRL(2019)·22 citations
40*
An alternative description of the weak lepton interaction
Konstantin Karplyuk🇺🇦 · Oleksandr Zhmudskyy🇺🇸
The description of the massive vector- and pseudo-vector bosons is proposed, which allows the use of them as interaction carriers. The boson propagators guarantee the renormalizability of the theory with massive intermediate bosons. The proposed description is free from the Englert-Brout-Higgs mechanism. These bosons are used to describe the weak lepton interactions. In such a description boson's and lepton's interaction Lagrangian coincides with the boson's and lepton's interaction Lagrangian in the Glashow-Weinberg-Salam model, which is in good agreement with the experimental results.
↳ physics.gen-phhep-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.