Wed·May 29, 2019Wednesday·May 29, 2019

1. 01*

   Heavy dark matter particle annihilation in dwarf spheroidal galaxies: radio signals at the SKA telescope

   Arpan Kar🇮🇳 · Sourav Mitra🇮🇳 · Biswarup Mukhopadhyaya🇮🇳 · Tirthankar Roy Choudhury🇮🇳

   A weakly interacting dark matter candidate is difficult to detect at high-energy colliders like the LHC, if its mass is close to, or higher than a TeV. On the other hand, pair-annihilation of such particles may give rise to $e^{+}{e}^{-}$ pairs in dwarf spheroidal galaxies (dSph), which in turn can lead to radio synchrotron signals that are detectable at the upcoming Square Kilometre Array (SKA) telescope within a moderate observation time. We investigate the circumstances under which this complementarity between collider and radio signals of dark matter can be useful in probing physics beyond the standard model of elementary particles. Both particle physics issues and the roles of diffusion and electromagnetic energy loss of the $e^{\pm }$ are taken into account. First, the criteria for detectability of trans-TeV dark matter are analysed independently of the particle physics model(s) involved. We thereafter use some benchmarks based on a popular scenario, namely, the minimal supersymmetric standard model. It is thus shown that the radio flux from a dSph like Draco should be observable in about 100 hours at the SKA, for dark matter masses upto 4-8 TeV. In addition, the regions in the space spanned by astrophysical parameters, for which such signals should be detectable at the SKA, are marked out.

   hep-phastro-ph.HEPRD(2020)·24 citations
2. 02*

   The Rise of SMEFT On-shell Amplitudes

   Rafael Aoude🇩🇪 · Camila S. Machado🇩🇪

   We present a map between the tree-level Standard Model Effective Theory (SMEFT) in the Warsaw basis and massive on-shell amplitudes. As a first step, we focus on the electroweak sector without fermions. We describe the Feynman rules for a particular choice of input scheme and compare them with the 3-point massive amplitudes in the broken phase. Thereby we fix an on-shell basis which allows us to study scattering amplitudes with recursion relations. We hope to open up new avenues of exploration to a complete formulation of massive EFTs in the on-shell language.

   hep-phJHEP(2019)·90 citations
3. 03*

   Two-loop triangle integrals with 4 scales for the $HZV$ vertex

   Yuxuan Wang🇨🇳 · Xiaofeng Xu🇨🇳 · Li Lin Yang🇨🇳

   We calculate analytically the two-loop triangle integrals entering the $\mathcal{O}(\alpha {\alpha }_s)$ corrections to the $HZV$ vertex with $V=Z^{\ast },{\gamma }^{\ast }$ using the method of differential equations. Our result provides a prototype to study the analytic properties of multi-loop multi-scale Feynman integrals, and also allows fast numeric evaluation for phenomenological studies. We apply our results to the leptonic decay of the Higgs boson and to $ZH$ production at electron-positron colliders. Besides the top quark loop, we include also the bottom quark loop contributions, whose evaluation takes a lot of time using purely numeric methods, but is very efficient with our analytic results.

   hep-phPRD(2019)·10 citations
4. 04*

   Novel Flavon Stabilization with Trimaximal Neutrino Mixing

   So Chigusa🇯🇵 · Shinta Kasuya🇯🇵 · Kazunori Nakayama🇯🇵

   We construct a supersymmetric $S_4$ flavor symmetry model with one of the trimaximal neutrino mixing patterns, the so-called TM${}_1$, by using the novel way to stabilize flavons, which we proposed recently. The flavons are assumed to have tachyonic supersymmetry breaking mass terms and stabilized by higher-dimensional terms in the potential. We can obtain the desired alignment structure of the flavon vacuum expectation values to realize neutrino masses and mixings consistent with the current observations. This mechanism naturally avoids the appearance of dangerous cosmological domain walls.

   hep-phPRD(2019)·3 citations
5. 05*

   Zee Model with Flavor Dependent Global $U(1)$ Symmetry

   Takaaki Nomura🇰🇷 · Kei Yagyu🇯🇵

   We study a simple extension of the Zee model, in which a discrete $Z_2$ symmetry imposed in the original model is replaced by a global $U(1)$ symmetry retaining the same particle content. Due to the $U(1)$ symmetry with flavor dependent charge assignments, the lepton sector has an additional source of flavor violating Yukawa interactions with a controllable structure, while the quark sector does not at tree level. We show that current neutrino oscillation data can be explained under constraints from lepton flavor violating decays of charged leptons in a successful charge assignment of the $U(1)$ symmetry. In such scenario, we find a characteristic pattern of lepton flavor violating decays of additional Higgs bosons, which can be a smoking gun signature at collider experiments.

   hep-phJHEP(2019)·11 citations
6. 06*

   On pseudorapidity distribution in p-Pb and Xe-Xe collisions at high energy based on the three-source Landau hydrodynamic model

   Li-Na Gao🇨🇳 · Zhen-Hu Li🇨🇳 · Er-Qin Wang🇨🇳

   The pseudorapidity distributions of charged particles produced in p-Pb collisions and Xe-Xe collisions at LHC energies are described by the revised Landau hydrodynamic model. The research results are in agreement with the experimental data measured by ALICE collaboration at LHC. The related parameters are obtained and analyzed. And, we extracted the values of the squared speed of sound for central source are between 0.4 and 0.5.

   hep-phnucl-thIndian J.Phys.(2021)·0 citations
7. 07*

   Questioning quark-gluon plasma formation in small collision systems

   Thomas A. Trainor🇺🇸

   A recent letter published in the journal Nature reports observation at the relativistic heavy ion collider (RHIC) of quark-gluon plasma (QGP) formation in small asymmetric collision systems denoted as $p$-Au, $d$-Au and ${}^3$He-Au. The claimed phenomenon, described as `short-lived QGP droplets,' is inferred from a combination of Glauber Monte Carlo simulations, measurement of two azimuth Fourier amplitudes $v_2$ and $v_3$ and hydro theory calculations. While that claim follows a trend in recent years to report `signals' conventionally attributed to QGP as appearing also in smaller collision systems, the new result remains surprising in the context of expectations before first RHIC operation that small systems, e.g. $d$-Au collisions, would provide control experiments in which a QGP was unlikely to appear. An alternative interpretation of the recent RHIC result is that small-system control experiments do convey an important message: The `signals' conventionally attributed to QGP formation in larger A-A collisions do not actually represent that phenomenon in any system. The present study reviews a broad array of experimental evidence for or against QGP formation in several collision systems. It examines in particular hydro theory descriptions of spectra and correlations usually interpreted to support QGP formation. Available evidence suggests that data features conventionally attributed to QGP formation represent either minimum-bias jet production or a nonjet azimuth quadrupole with properties inconsistent with a hydro hypothesis.

   hep-phnucl-th6 citations
8. 08*

   Dynamical generation of quark/lepton mass hierarchy in an extra dimension

   Yukihiro Fujimoto🇯🇵 · Kouhei Hasegawa🇯🇵 · Kenji Nishiwaki🇭🇷 · Makoto Sakamoto🇯🇵 · Kazunori Takenaga🇯🇵 · Pedro Hugo Tanaka🇯🇵 · Inori Ueba🇯🇵

   We show that the observed quark/lepton mass hierarchy can be realized dynamically on an interval extra dimension with point interactions. In our model, the positions of the point interactions play a crucial role to control the quark/lepton mass hierarchy and are determined by the minimization of the Casimir energy. By use of the exact extra-dimensional coordinate-dependent vacuum expectation value of a gauge singlet scalar, we find that there is a parameter set, where the positions of the point interactions are stabilized and fixed, which can reproduce the experimental values of the quark masses precisely enough, while the charged lepton part is less relevant. We also show that possible mixings among the charged leptons will improve the situation significantly.

   hep-phhep-thPTEP(2019)·5 citations
9. 09*

   Trace and axial anomalies on equal footing

   Renata Jora🇷🇴

   We discuss for some particular non supersymmetric theories a generalized symmetry that includes both the scale and axial transformations and leads to a single current that may contain also a pseudoscalar term. The method, inspired by the superconformal anomalies has important application for low energy effective models where it allows the introduction of a single complex glueball field with a scalar and a pseudoscalar component on the same footing with the complex meson nonets fields made of quarks. Both axial and trace and axial anomalies are satisfied in accordance to the meson structure and the QCD requirements.

   hep-phAdv.High Energy Phys.(2020)·0 citations
10. 10*

    Strong isospin symmetry breaking in light scalar meson production

    N.N. Achasov🇷🇺 · G.N. Shestakov🇷🇺

    Isospin symmetry breaking is discussed as a tool for studying the nature and production mechanisms of light scalar mesons. We are concerned with isospin breaking effects with an amplitude $\sim \sqrt{m_d-m_u}$ (instead of the usual $\sim m_d-m_u$), where $m_u$ and $m_d$ are the $u$ and $d$ quark masses, whose magnitude and phase vary with energy in a resonance-like way characteristic of the $K\bar{K}$ threshold region. We consider a variety of reactions that can experimentally reveal (or have revealed) the mixing of $a_0^0(980)$ and $f_0(980)$ resonances that breaks the isotopic invariance due to the mass difference between $K^{+}$ and $K^0$ mesons. Experimental results on the search for $a_0^0(980)-f_0(980)$ mixing in $f_1(1285)\to f_0(980){\pi }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ and $\eta (1405)\to f_0(980){\pi }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decays suggest a broader perspective on the isotopic symmetry breaking effects due to the $K^{+}$ and $K^0$ mass difference. It has become clear that not only the $a_0^0(980)-f_0(980)$ mixing but also any mechanism producing $K\bar{K}$ pairs with a definite isospin in an S wave gives rise to such effects, thus suggesting a new tool for studying the nature and production mechanisms of light scalars. Of particular interest is the case of a large isotopic symmetry breaking in the $\eta (1405)\to f_0(980){\pi }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decay due to the occurrence of anomalous Landau thresholds (logarithmic triangle singularities), i.e., due to the $\eta (1405)\to (K^{\ast }\bar{K}+{\bar{K}}^{\ast }K)\to (K^{+}{K}^{-}+K^0{\bar{K}}^0){\pi }^0\to f_0(980){\pi }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ transition (where it is of fundamental importance that the $K^{\ast }$ meson has a finite width).

    hep-phhep-exnucl-thPhys.Usp.(2019)·14 citations
11. 11*

    Weak decays of doubly heavy baryons: decays to system of $\pi$ mesons

    A. S. Gerasimov🇷🇺 · A. V. Luchinsky🇷🇺

    In the presented article we consider exclusive weak decays of doubly heavy baryons with spin $J=1/2$ with production of leptonic pair or a set of light mesons. Using QCD factorization theorem and spectral functions approach we obtain theoretical predictions for the partial probabilities of these decays and distributions over various kinematic variables. According to the obtaining results partial probabilities of some of researched decays are large enough to be observed experimentally.

    hep-phPRD(2019)·27 citations
12. 12*

    Hidden relations in three generation seesaw model with Dirac mass matrix of four-zero texture

    Takuya Morozumi🇯🇵 · Yusuke Shimizu🇯🇵 · Hiroyuki Umeeda🇹🇼 · Akihiro Yuu🇯🇵

    We present predictions for CP violating phases of the Type-I seesaw model with four-zero textures on the Dirac mass matrix. For the four-zero textures, the effective low energy Majorana mass matrix is parametrized with seven parameters. They are three mass-dimensional parameters, two angles and two CP violating sources. The number of these parameters is less than that of the general description of the Majorana mass matrix with three neutrino masses, three mixing angles and three CP violating phases. In particular, only two independent CP violating sources give rise to three CP violating phases. The efficient and comprehensive method is proposed in this paper to investigate four-zero textures in Type-I seesaw. We numerically show the possible range of CP violating phases in the plane of a Dirac CP violating phase and one of Majorana phases. Some cases show the strong correlations among two phases. These correlations can be explained by hidden relations among the elements of Majorana matrix with the four-zero textures. The hidden relations are classified according to the position of one vanishing off-diagonal element of Majorana mass matrix. The Majorana mass matrix all of whose elements are non-vanishing also produces other hidden relations particularly in the case of four-zero textures. By applying the hidden relations, we describe the concrete correlations among CP violating phases.

    hep-phPLB(2019)·2 citations
13. 13*

    Properties of excited $B_c$ states in QCD

    T.M.Aliev🇹🇷 · T.Barakat🇸🇦 · S.Bilmis🇹🇷

    The mass and leptonic decay constants of recently observed two new excited $B_c$ states at LHC are studied within the QCD sum rules. Considering the contributions of the ground and radially excited states, the mass and residues of the excited states of pseudoscalar and vector mesons are calculated in the framework of two different approaches of the QCD sum rules, namely, linear combinations of the corresponding sum rules and its derivatives as well as QCD sum rules with the incorporation of the least square fitting method. The obtained results on mass $m_{B_c^{+}}(2S)=6.88\pm 0.03\mathrm{GeV}$ and $m_{B_c^{\ast +}}(2S)=6.94\pm 0.03\mathrm{GeV}$ are in good agreement with the experimental data. Our predictions for the decay constants of these states are: $f_{B_c^{+}}(2S)=0.42\pm 0.02\mathrm{GeV}$ and $f_{B_c^{\ast +}}(2S)=0.46\pm 0.01\mathrm{GeV}$, which can be checked at future experiments to be conducted at the LHC. Comparison of our results with the predictions of the other approaches on mass and residues is also presented.

    hep-phNPB(2019)·13 citations
14. 14*

    Next-to-leading power threshold effects for resummed prompt photon production

    Melissa van Beekveld🇳🇱 · Wim Beenakker🇳🇱 · Rahul Basu🇮🇳 · Eric Laenen🇳🇱 · Anuradha Misra🇮🇳 · Patrick Motylinski🇩🇪

    We assess and compare different methods for including leading threshold logarithms at next-to-leading-power in prompt photon production at hadron colliders, for both the direct and parton fragmentation mechanisms. We do this in addition to next-to-leading logarithmic threshold and joint resummation at leading power. We study the size of these effects and their scale variations for LHC kinematics. We find that the next-to-leading power effects have a noticeable effect on the photon transverse momentum distribution, typically of order $\mathcal{O}(10\%)$, depending on the method of inclusion. Our results indicate that next-to-leading power terms can reduce the scale dependence of the distribution considerably.

    hep-phPRD(2019)·39 citations
15. 15*

    The direct CP violation in a general two Higgs doublet model

    Syuhei Iguro🇯🇵 · Yuji Omura🇯🇵

    In this paper, we study the CP violating processes in a general two-Higgs-doublet model (2HDM) with tree-level flavor changing neutral currents. In this model, sizable Yukawa couplings involving top and charm quarks are still allowed by the collider and flavor experiments, while the other couplings are strongly constrained experimentally. The sizable couplings, in general, have imaginary parts and could largely contribute to the CP violating observables concerned with the $B$ and $K$ mesons. In particular, the contribution may be so large that it affects the direct CP violating $K$ meson decay, where the discrepancy between the experimental result and the Standard Model prediction is reported. We discuss how well the anomaly is resolved in the 2HDM, based on study of the other flavor observables. We also propose the way to test our 2HDM at the LHC.

    hep-phhep-exJHEP(2019)·21 citations
16. 16*

    Heavy neutrino production via $Z^{\prime }$ at the lifetime frontier

    Frank F. Deppisch🇬🇧 · Suchita Kulkarni🇦🇹 · Wei Liu🇬🇧

    We investigate the pair production of right-handed neutrinos from the decay of an additional neutral $Z^{\prime }$ boson in the gauged $B-L$ model. Taking into account current constraints on the $Z^{\prime }$ mass and the associated gauge coupling $g_1^{\prime }$, we analyse the sensitivity of proposed experiments at the lifetime frontier, FASER 2, CODEX-b, MATHUSLA as well as a hypothetical version of the MAPP detector to a long lived heavy neutrino $N$ originating in the decays of the $Z^{\prime }$. We further complement this study with determining the reach of LHCb and a CMS-type detector for the high-luminosity LHC run. We demonstrate that in a background free scenario with $g_1^{\prime }=10^{-3}$ near the current limit, FASER 2 is sensitive to the active-sterile neutrino mixing down to $V_{\mu N}\approx 10^{-4}$, while a reach of $V_{\mu N}\approx 10^{-5}$ can be obtained for CODEX-b and LHCb, in a mass regime of $m_N\approx 5-20$ GeV and $m_{Z^{\prime }}\approx 20-70$ GeV. Finally, MATHUSLA can probe $V_{\mu N}\approx 10^{-7}$ and cover the mixing regime expected in a canonical seesaw scenario of light neutrino mass generation.

    hep-phPRD(2019)·96 citations
17. 17*

    Generalised CP Symmetry in Modular-Invariant Models of Flavour

    P. P. Novichkov🇮🇹 · J. T. Penedo🇵🇹 · S. T. Petcov🇮🇹 · A. V. Titov🇬🇧

    The formalism of combined finite modular and generalised CP (gCP) symmetries for theories of flavour is developed. The corresponding consistency conditions for the two symmetry transformations acting on the modulus $\tau$ and on the matter fields are derived. The implications of gCP symmetry in theories of flavour based on modular invariance described by finite modular groups are illustrated with the example of a modular $S_4$ model of lepton flavour. Due to the addition of the gCP symmetry, viable modular models turn out to be more constrained, with the modulus $\tau$ being the only source of CP violation.

    hep-phhep-thJHEP(2019)·210 citations
18. 18*

    Electroweak Baryogenesis from Temperature-Varying Couplings

    Sebastian A. R. Ellis🇺🇸 · Seyda Ipek🇺🇸 · Graham White🇨🇦

    The fundamental couplings of the Standard Model are known to vary as a function of energy scale through the Renormalisation Group (RG), and have been measured at the electroweak scale at colliders. However, the variation of the couplings as a function of temperature need not be the same, raising the possibility that couplings in the early universe were not at the values predicted by RG evolution. We study how such temperature-variance of fundamental couplings can aid the production of a baryon asymmetry in the universe through electroweak baryogenesis. We do so in the context of the Standard Model augmented by higher-dimensional operators up to dimension 6.

    hep-phJHEP(2019)·56 citations
19. 19*

    CP Symmetries as Guiding Posts: revamping tri-bi-maximal Mixing. Part II

    Peng Chen🇨🇳 · Salvador Centelles Chuliá🇪🇸 · Gui-Jun Ding🇨🇳 · Rahul Srivastava🇪🇸 · José W. F. Valle🇪🇸

    In this follow up of arXiv:1812.04663 we analyze the generalized CP symmetries of the charged lepton mass matrix compatible with the complex version of the Tri-Bi-Maximal (TBM) lepton mixing pattern. These symmetries are used to `revamp' the simplest TBM \textit{Ansatz} in a systematic way. Our generalized patterns share some of the attractive features of the original TBM matrix and are consistent with current oscillation experiments. We also discuss their phenomenological implications both for upcoming neutrino oscillation and neutrinoless double beta decay experiments.

    hep-phhep-exPRD(2019)·14 citations
20. 20*

    Chiral phase transition in (2 + 1)-flavor QCD

    Heng-Tong Ding🇨🇳 · Prasad Hegde🇮🇳 · Olaf Kaczmarek🇩🇪 · Frithjof Karsch🇩🇪 · Anirban Lahiri🇩🇪 · Sheng-Tai Li🇨🇳 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸

    The chiral phase transition temperature $T_c^0$ is a fundamental quantity of QCD. To determine this quantity we have performed simulations of (2 + 1)-flavor QCD using the Highly Improved Staggered Quarks (HISQ/tree) action on $N_{\tau }=6,8$ and 12 lattices with aspect ratios $N_{\sigma }/N_{\tau }$ ranging from 4 to 8. In our simulations the strange quark mass is fixed to its physical value $m_s^{\mathrm{phy}}$, and the values of two degenerate light quark masses $m_l$ are varied from $m_s^{\mathrm{phy}}/20$ to $m_s^{\mathrm{phy}}/160$ which correspond to a Goldstone pion mass $m_{\pi }$ ranging from 160 MeV to 55 MeV in the continuum limit. By investigating the light quark mass dependence and the volume dependence of various chiral observables, e.g. chiral susceptibilities and Binder cumulants, no evidence for a first order phase transition in our current quark mass window is found. Two estimators $T_{60}$ and $T_{\delta }$ are proposed to extract the chiral phase transition temperature $T_c^0$ in the chiral and continuum limit and our current estimate for $T_c^0$ is $132_{-6}^{+3}$ MeV.

    ↳ hep-lathep-phhep-thnucl-thPoS(2019)·14 citations
21. 21*

    Extended supersymmetry with central charges in Dirac action with curved extra dimensions

    Inori Ueba🇯🇵

    We discuss a new realization of $\mathcal{N}$-extended quantum-mechanical supersymmetry (QM SUSY) with central charges hidden in the four-dimensional (4D) mass spectrum of higher dimensional Dirac action with curved extra dimensions. We show that this $\mathcal{N}$-extended QM SUSY results from symmetries in extra dimensions, and the supermultiplets in this supersymmetry algebra correspond to the Bogomol'nyi--Prasad--Sommerfield states. Furthermore, we examine the model of the $S^2$ extra dimension with a magnetic monopole background and confirm that the $\mathcal{N}$-extended QM SUSY explains the degeneracy of the 4D mass spectrum.

    ↳ hep-thhep-phquant-phPRD(2019)·5 citations
22. 22*

    Standard model Higgs field and hidden sector cosmology

    Tommi Tenkanen🇺🇸

    We consider scenarios where the inflaton field decays dominantly to a hidden dark matter (DM) sector. By studying the typical behavior of the Standard Model (SM) Higgs field during inflation, we derive a relation between the primordial tensor-to-scalar ratio $r$ and amplitude of the residual DM isocurvature perturbations $\beta$ which is typically generated if the DM is thermally decoupled from the SM sector. We consider different expansion histories and find that if the Universe was radiation- or matter-dominated after inflation, a future discovery of primordial DM isocurvature will rule out all simple scenarios of this type because generating observable $\beta$ from the Higgs is not possible without violating the bounds on $r$. Seen another way, the Higgs field is generically not a threat to models where both the inflaton and DM reside in a decoupled sector. However, this is not necessarily the case for an early kination-dominated epoch, as then the Higgs can source sizeable $\beta$. We also discuss why the Higgs cannot source the observed curvature perturbation at large scales in any of the above cases but how the field can still be the dominant source of curvature perturbations at small scales.

    ↳ astro-ph.COgr-qchep-phPRD(2019)·19 citations
23. 23*

    Looking for ultralight dark matter near supermassive black holes

    Nitsan Bar🇮🇱 · Kfir Blum🇮🇱 · Thomas Lacroix🇪🇸 · Paolo Panci🇨🇭

    Measurements of the dynamical environment of supermassive black holes (SMBHs) are becoming abundant and precise. We use such measurements to look for ultralight dark matter (ULDM), which is predicted to form dense cores ("solitons") in the centre of galactic halos. We search for the gravitational imprint of an ULDM soliton on stellar orbits near Sgr A* and by combining stellar velocity measurements with Event Horizon Telescope imaging of M87*. Finding no positive evidence, we set limits on the soliton mass for different values of the ULDM particle mass $m$. The constraints we derive exclude the solitons predicted by a naive extrapolation of the soliton-halo relation, found in DM-only numerical simulations, for $2\times 10^{-20}\mathrm{eV}\lesssim m\lesssim 8\times 10^{-19}\mathrm{eV}$ (from Sgr A*) and $m\lesssim 4\times 10^{-22}\mathrm{eV}$ (from M87*). However, we present theoretical arguments suggesting that an extrapolation of the soliton-halo relation may not be adequate: in some regions of the parameter space, the dynamical effect of the SMBH could cause this extrapolation to over-predict the soliton mass by orders of magnitude.

    ↳ astro-ph.COhep-phJCAP(2019)·106 citations
24. 24*

    Saving Tachyons in Open String Theory

    Taejin Lee🇰🇷

    Using string scattering amplitudes of open bosonic string on a single $D$-brane, we construct a local field theoretical action for tachyon fields. Cubic local interactions between various particles, belonging to the particle spectrum of string may be directly followed from three-string scattering amplitude. These cubic local interactions may generate perturbative non-local four-particle interactions, which may contribute to four-string scattering amplitude. It was observed that tachyon field in open bosonic string theory must be represented by a complex field in order to reproduce the Veneziano amplitude, describing four-tachyon scattering. The Veneziano amplitude, expanded in terms of $s$-channel poles was compared with the four-tachyon scattering amplitudes in $s$-channel generated perturbatively and it was found that a quartic potential term is needed in the local field theoretical action, which describes open string theory effectively in the low energy regime. With this quartic term, the tachyon potential has a stable minimum point and the tachyon field may condensate. As a result, both tachyon and gauge fields become massive at Planck scale and completely disappear from the low energy particle spectrum.

    ↳ hep-thhep-ph0 citations
25. 25*

    Ability of LIGO and LISA to probe the equation of state of the early Universe

    Daniel G. Figueroa🇨🇭 · Erwin H. Tanin🇨🇭

    The expansion history of the Universe between the end of inflation and the onset of radiation-domination (RD) is currently unknown. If the equation of state during this period is stiffer than that of radiation, $w>1/3$, the gravitational wave (GW) background from inflation acquires a blue-tilt $\frac{d\log {\rho }_{\mathrm{GW}}}{d\log f}=\frac{2(w-1/3)}{(w+1/3)}>0$ at frequencies $f\gg f_{\mathrm{RD}}$ corresponding to modes re-entering the horizon during the stiff-domination (SD), where $f_{\mathrm{RD}}$ is the frequency today of the horizon scale at the SD-to-RD transition. We characterized in detail the transfer function of the GW energy density spectrum, considering both 'instant' and smooth modelings of the SD-to-RD transition. The shape of the spectrum is controlled by $w$, $f_{\mathrm{RD}}$, and $H_{\inf }$ (the Hubble scale of inflation). We determined the parameter space compatible with a detection of this signal by LIGO and LISA, including possible changes in the number of relativistic degrees of freedom, and the presence of a tensor tilt. Consistency with upper bounds on stochastic GW backgrounds, however, rules out a significant fraction of the observable parameter space. We find that this renders the signal unobservable by Advanced LIGO, in all cases. The GW background remains detectable by LISA, though only in a small island of parameter space, corresponding to scenarios with an equation of state in the range $0.46\lesssim w\lesssim 0.56$ and a high inflationary scale $H_{\inf }\gtrsim 10^{13}\mathrm{GeV}$, but low reheating temperature $1\mathrm{MeV}\lesssim T_{\mathrm{RD}}\lesssim 150\mathrm{MeV}$ (equivalently, $10^{-11}\mathrm{Hz}\lesssim f_{\mathrm{RD}}\lesssim 3.6\cdot 10^{-9}\mathrm{Hz}$). Implications for early Universe scenarios resting upon an SD epoch are briefly discussed.

    ↳ astro-ph.COgr-qchep-phJCAP(2019)·146 citations
26. 26*

    Poincaré constraints on the gravitational form factors for massive states with arbitrary spin

    Sabrina Cotogno🇫🇷 · Cédric Lorcé🇫🇷 · Peter Lowdon🇫🇷

    In this work we analyse the constraints imposed by Poincaré symmetry on the gravitational form factors appearing in the Lorentz decomposition of the energy-momentum tensor matrix elements for massive states with arbitrary spin. By adopting a distributional approach, we prove for the first time non-perturbatively that the zero momentum transfer limit of the leading two form factors in the decomposition are completely independent of the spin of the states. It turns out that these constraints arise due to the general Poincaré transformation and on-shell properties of the states, as opposed to the specific characteristics of the individual Poincaré generators themselves. By expressing these leading form factors in terms of generalised parton distributions, we subsequently derive the linear and angular momentum sum rules for states with arbitrary spin.

    ↳ hep-thgr-qchep-phPRD(2019)·31 citations
27. 27*

    Effects of polarization and high harmonics of two-color fields on dynamically assisted pair production

    Obulkasim Olugh🇨🇳 · Zi-Liang Li🇨🇳 · Bai-Song Xie🇨🇳

    Electron-positron pair production in dynamically assisted two-color electric fields is investigated for various polarizations. Momentum spectrum and number density of the created pairs are examined carefully, in particular, the effects of polarization and high harmonics of two-color fields are exhibited. For only single strong field, the interference effects of momentum spectrum would vanish when polarization is high, however, for the dynamical assisted two-color fields, the interference effects would be more and more remarkable with polarization. The multiple peaks of momentum spectrum in elliptic or/and circular polarization are observed and explained. It is found that there exists a strong nonlinear dependence of the number density on the high harmonics of two-color fields, for example, the number density can be enhanced significantly over $7-8$ orders when appropriate high harmonics is present. Another interesting finding is that the polarization effect on number density is gradually weaken as the high harmonics increases, however, a weak nonlinearity relation appears again if the high harmonics exceeds a single-photon threshold.

    ↳ quant-phhep-phPLB(2020)·21 citations
28. 28*

    A Robust Method for Treating Astrophysical Mismodeling in Dark Matter Annihilation Searches of Dwarf Spheroidal Galaxies

    Tim Linden🇺🇸

    Fermi-LAT observations have strongly constrained dark matter annihilation through the joint-likelihood analysis of dwarf spheroidal galaxies (dSphs). These constraints are expected to be robust because dSphs have measurable dark matter content and produce negligible astrophysical emission. However, each dSph is dim, with a predicted flux that typically falls below the accuracy of the background model. We show that this significantly diminishes the reliability of previous joint-likelihood algorithms, and develop an improved analysis that directly accounts for the effect of background mismodeling. This method produces more robust limits and detections of dark matter in both real and mock data. We calculate improved limits on the dark matter annihilation cross-section, which differ by nearly a factor of two from previous analyses - despite examining identical data.

    ↳ astro-ph.HEastro-ph.GAhep-phPRD(2020)·13 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.