Wed·Mar 23, 2016Wednesday·March 23, 2016

1. 01*

   Universal Strangeness Production in Hadronic and Nuclear Collisions

   P.Castorina🇮🇹 · S.Plumari🇮🇹 · H.Satz🇩🇪

   We show that strangeness suppression in hadronic and nuclear collisions is fully determined by the initial energy density of the collision. The suppression factor ${\gamma }_s(s)$, with $\sqrt{s}$ denoting the collision energy, can be expressed as a universal function of the initial energy density ${ϵ}_0(s)$, and the resulting pattern is in excellent agreement with data from $p-p,p-Pb,Cu-Cu,Au-Au$ and $Pb-Pb$ data over a wide range of energies and for different centralities.

   hep-phnucl-thIJMPE(2016)·22 citations
2. 02*

   Gluon TMD in particle production from low to moderate x

   I. Balitsky🇺🇸 · A. Tarasov🇺🇸

   We study the rapidity evolution of gluon transverse momentum dependent distributions appearing in processes of particle production and show how this evolution changes from small to moderate Bjorken x.

   hep-phJHEP(2016)·112 citations
3. 03*

   Comments on the diphoton excess: critical reappraisal of effective field theory interpretations

   Jernej F. Kamenik🇸🇮 · Benjamin R. Safdi🇺🇸 · Yotam Soreq🇺🇸 · Jure Zupan🇺🇸

   We consider the diphoton excess observed by ATLAS and CMS using the most up-to-date data and estimate the preferred enhancement in the production rate between 8 TeV and 13 TeV. Within the framework of effective field theory (EFT), we then show that for both spin-0 and spin-2 Standard Model (SM) gauge-singlet resonances, two of the three processes S to ZZ, S to Z gamma, and S to WW must occur with a non-zero rate. Moreover, we demonstrate that these branching ratios are highly correlated in the EFT. Couplings of S to additional SM states may be constrained and differentiated by comparing the S production rates with and without the vector-boson fusion (VBF) cuts. We find that for a given VBF to inclusive production ratio there is maximum rate of S to gauge bosons, b b-bar, and lighter quark anti-quark pairs. Simultaneous measurements of the width and the VBF ratio may be able to point towards the existence of hidden decays.

   hep-phhep-exJHEP(2016)·31 citations
4. 04*

   Search for Sphalerons: IceCube vs. LHC

   John Ellis🇬🇧 · Kazuki Sakurai🇬🇧 · Michael Spannowsky🇬🇧

   We discuss the observability of neutrino-induced sphaleron transitions in the IceCube detector, encouraged by a recent paper by Tye and Wong (TW), which argued on the basis of a Bloch wave function in the periodic sphaleron potential that such transitions should be enhanced compared to most previous calculations. We calculate the dependence on neutrino energy of the sphaleron transition rate, comparing it to that for conventional neutrino interactions, and we discuss the observability of tau and multi-muon production in sphaleron-induced transitions. We use IceCube 4-year data to constrain the sphaleron rate, finding that it is comparable to the upper limit inferred previously from a recast of an ATLAS search for microscopic black holes at the LHC with $\sim 3$/fb of collisions at 13 TeV. The IceCube constraint is stronger for a sphaleron barrier height $E_{\mathrm{Sph}}\gtrsim 9$ TeV, and would be comparable with the prospective LHC sensitivity with 300/fb of data at 14 TeV if $E_{\mathrm{Sph}}\sim 11$ TeV.

   hep-phhep-exhep-thJHEP(2016)·56 citations
5. 05*

   Ultralight Repulsive Dark Matter and BEC

   JiJi Fan🇺🇸

   Ultralight scalar dark matter with mass at or below the eV scale and pressure from repulsive self-interaction could form a Bose-Einstein condensate in the early Universe and maybe in galaxies as well. It has been suggested to be a possible solution to the cusp/core problem or even to explain MOND phenomenology. In this paper, I initiate a study of possible self-interactions of ultralight scalar dark matter from the particle physics point of view. To protect its mass, the scalar dark matter is identified as a pseudo Nambu-Goldstone boson (pNGB). Quite a few pNGB models with different potentials such as the QCD axion and the dilaton lead to attractive self-interactions. Yet if an axion is a remnant of a 5D gauged U(1) symmetry, its self-interactions could be repulsive provided the masses and charges of the 5D matter contributing to its potential satisfy certain constraints. Collective symmetry breaking could also lead to a repulsive self-interaction yet with too large a strength that is ruled out by Bullet Cluster constraints. I also discuss cosmological and astrophysical constraints on ultralight repulsive dark matter in terms of a parametrization motivated by particle physics considerations.

   hep-phastro-ph.COastro-ph.GAPhys.Dark Univ.(2016)·125 citations
6. 06*

   Flavor hierarchies from dynamical scales

   Giuliano Panico🇪🇸 · Alex Pomarol🇪🇸

   One main obstacle for any beyond the SM (BSM) scenario solving the hierarchy problem is its potentially large contributions to electric dipole moments. An elegant way to avoid this problem is to have the light SM fermions couple to the BSM sector only through bilinears, $\bar{f}f$. This possibility can be neatly implemented in composite Higgs models. We study the implications of dynamically generating the fermion Yukawa couplings at different scales, relating larger scales to lighter SM fermions. We show that all flavor and CP-violating constraints can be easily accommodated for a BSM scale of few TeV, without requiring any extra symmetry. Contributions to B physics are mainly mediated by the top, giving a predictive pattern of deviations in $\Delta F=2$ and $\Delta F=1$ flavor observables that could be seen in future experiments.

   hep-phJHEP(2016)·105 citations
7. 07*

   Higgs--Flavon Mixing and $h\to \mu \tau$

   Katri Huitu🇫🇮 · Venus Keus🇫🇮 · Niko Koivunen🇫🇮 · Oleg Lebedev🇫🇮

   ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, $h\to \mu \tau$. We show that this result can be accommodated through a mixing of the Higgs with a flavon, the field responsible for generating the Yukawa matrices in the lepton sector. We employ a version of the Froggatt-Nielsen mechanism at the electroweak scale, with only the leptons and the flavon transforming non--trivially under the corresponding symmetry group. Non--observation of charged lepton flavor violation (LFV) in other processes imposes important constraints on the model, which we find to be satisfied in substantial regions of parameter space.

   hep-phJHEP(2016)·51 citations
8. 08*

   Nucleon Helicity and Transversity Parton Distributions from Lattice QCD

   Jiunn-Wei Chen🇹🇼 · Saul D. Cohen🇺🇸 · Xiangdong Ji🇨🇳 · Huey-Wen Lin🇺🇸 · Jian-Hui Zhang🇩🇪

   We present the first lattice-QCD calculation of the isovector polarized parton distribution functions (both helicity and transversity) using the large-momentum effective field theory (LaMET) approach for direct Bjorken-$x$ dependence. We first review the detailed steps of the procedure in the unpolarized case, then generalize to the helicity and transversity cases. We also derive a new mass-correction formulation for all three cases. We then compare the effects of each finite-momentum correction using lattice data calculated at $M_{\pi }\approx 310$ MeV. Finally, we discuss the implications of these results for the poorly known antiquark structure and predict the sea-flavor asymmetry in the transversely polarized nucleon.

   hep-phhep-latNPB(2016)·245 citations
9. 09*

   Lepton flavor violating Higgs boson decay $h\to \mu \tau$ at the ILC

   Indrani Chakraborty🇮🇳 · Amitava Datta🇮🇳 · Anirban Kundu🇮🇳

   We study the possible reach of the proposed International Linear Collider (ILC) in exploring the lepton flavor violating (LFV) Higgs boson decay $h\to \mu \tau$. Two generic types of models are investigated, both involving an extended scalar sector. For the first type, the rest of the scalars are heavy and beyond the reach of ILC but the LFV decay occurs through a tiny admixture of the Standard Model (SM) doublet with the heavy degrees of freedom. In the second class, which is more constrained from the existing data, the SM Higgs boson does not have any LFV decay but there are other scalars degenerate with it that gives rise to the LFV signal. We show that ILC can pin down the branching fraction of $h\to \mu \tau$, and hence the effective LFV Yukawa coupling, to a very small value, due to the fact that there are signal channels with unlike flavor leptons but no missing energy. It turns out that the low-energy options of the ILC, namely, $\sqrt{s}=250$ or 500 GeV are better to investigate such channels, and the option of beam polarization helps too. At least an order of magnitude improvement is envisaged over the existing limits.

   hep-phJ.Phys.G(2016)·22 citations
10. 10*

    Study of ${\Lambda }_b\to \Lambda (\varphi ,{\eta }^{(\prime )})$ and ${\Lambda }_b\to \Lambda K^{+}{K}^{-}$ decays

    C.Q. Geng🇨🇳 · Y.K. Hsiao🇨🇳 · Yu-Heng Lin🇹🇼 · Yao Yu🇨🇳

    We study the charmless two-body ${\Lambda }_b\to \Lambda (\varphi ,{\eta }^{(\prime )})$ and three-body ${\Lambda }_b\to \Lambda K^{+}{K}^{-}$ decays. We obtain $\mathcal{B}({\Lambda }_b\to \Lambda \varphi )=(3.53\pm 0.24)\times 10^{-6}$ to agree with the recent LHCb measurement. However, we find that $\mathcal{B}({\Lambda }_b\to \Lambda (\varphi \to )K^{+}{K}^{-})=(1.71\pm 0.12)\times 10^{-6}$ is unable to explain the LHCb observation of $\mathcal{B}({\Lambda }_b\to \Lambda K^{+}{K}^{-})=(15.9\pm 1.2\pm 1.2\pm 2.0)\times 10^{-6}$, which implies the possibility for other contributions, such as that from the resonant ${\Lambda }_b\to K^{-}{N}^{\ast },N^{\ast }\to \Lambda K^{+}$ decay with $N^{\ast }$ as a higher-wave baryon state. For ${\Lambda }_b\to \Lambda {\eta }^{(\prime )}$, we show that $\mathcal{B}({\Lambda }_b\to \Lambda \eta ,\Lambda {\eta }^{\prime })=(1.47\pm 0.35,1.83\pm 0.58)\times 10^{-6}$, which are consistent with the current data of $(9.3_{-5.3}^{+7.3},<3.1)\times 10^{-6}$, respectively. Our results also support the relation of $\mathcal{B}({\Lambda }_b\to \Lambda \eta )\simeq \mathcal{B}({\Lambda }_b\to \Lambda {\eta }^{\prime })$, given by the previous study.

    hep-phhep-exEPJC(2016)·15 citations
11. 11*

    Configuration mixings and light-front relativistic quark model predictions for the electroexcitation of the Delta(1232)3/2+, N(1440)1/2+, and Delta(1600)3/2+

    I. G. Aznauryan🇺🇸 · V. D. Burkert🇺🇸

    We investigate the impact of the configurations mixings that follow from QCD-inspired interquark forces on our results for the electroexcitation of the Delta(1232)3/2+, N(1440)1/2+, and Delta(1600)3/2+ obtained earlier in the light-front relativistic quark model. We have shown that the configurations mixings increase the 3q contribution to the gamma* N -> Delta(1232)3/2+ magnetic-dipole form factor at Q2=0 from 42% to 63% and significantly improve the agreement with experiment for the gamma* p -> N(1440)1/2+ transverse helicity amplitude at Q2 > 1.5GeV2. For the gamma* N -> Delta(1600)3/2+ transition, configuration mixings change strongly the results obtained earlier for the N and Delta(1600)3/2+ taken as pure states in the multiplets [56,0+] and [56',0+].

    hep-ph20 citations
12. 12*

    $\Delta$ self-energy at finite temperature and density and the $\pi N$ cross-section

    Snigdha Ghosh🇮🇳 · Sourav Sarkar🇮🇳 · Sukanya Mitra🇮🇳

    The self energy of $\Delta$-baryon is evaluated at finite temperature and density using the real time formalism of thermal field theory. The Dyson-Schwinger equation is used to get the exact thermal propagator followed by the spectral function of $\Delta$. The $\pi N$ scattering cross section obtained using explicit $\Delta$ exchange is normalized to the experimental data in vacuum and its medium modification is implemented by means of the exact thermal propagator. A significant suppression of the peak of the cross-section is observed at higher temperature and baryon density. Effects on the mean relaxation time of nucleons and the temperature dependence of the shear viscosity of a pion nucleon gas are demonstrated.

    hep-phnucl-thPRD(2017)·11 citations
13. 13*

    Neutrino Mass Matrices from Two Zero 3x2 Yukawa Textures and Minimal d=5 Entries

    Avtandil Achelashvili🇬🇪 · Zurab Tavartkiladze🇬🇪

    Aiming to relate leptonic CP violating phase $\delta$ to the cosmological CP asymmetry, we study the extension of MSSM by two quasi-degenerate (strictly degenerate at tree level) right-handed neutrinos and consider all possible two texture zero 3x2 Yukawa matrices plus one $\Delta L=2$ dimension five (d=5) operator contributing to the light neutrino mass matrix. We classify all experimentally viable mass matrices, leading to several predictions, and analytically derive predictive relations. We also relate the CP violating $\delta$ phase to the CP phase of the thermal leptogenesis.

    hep-phInt.J.Mod.Phys.A(2016)·6 citations
14. 14*

    Improving naturalness in Gauge Mediation with non-unified messenger sectors

    Lorenzo Calibbi🇨🇳 · Tianjun Li🇨🇳 · Azar Mustafayev🇺🇸 · Shabbar Raza🇨🇳

    We study models of gauge-mediated supersymmetry breaking with messengers that do not belong to complete representations of grand-unified gauge groups. We show that certain setups characterized by heavy Wino can greatly improve the fine tuning with respect to models with unified messengers, such as minimal gauge mediation. The typical models with low tuning feature multi-TeV superparticles, with the exception of the Higgsinos and possibly Bino and right-handed sleptons. As a consequence, the absence of signals for supersymmetry at the LHC is trivially accommodated in our framework. On the other hand, testing these models will be challenging at the LHC. We finally show that the gravitino can be a consistent candidate for cold dark matter, provided a rather low reheating temperature, if a standard thermal history of the universe is assumed.

    hep-phPRD(2016)·12 citations
15. 15*

    New approach to the resummation of logarithms in Higgs-boson decays to a vector quarkonium plus a photon

    Geoffrey T. Bodwin🇺🇸 · Hee Sok Chung (Argonne)🇨🇭 · June-Haak Ee🇰🇷 · Jungil Lee (Korea U.)🇰🇷

    We present a calculation of the rates for Higgs-boson decays to a vector heavy-quarkonium state plus a photon, where the heavy quarkonium states are the J/psi and the Upsilon(nS) states, with n=1, 2, or 3. The calculation is carried out in the light-cone formalism, combined with nonrelativistic QCD factorization, and is accurate at leading order in m_Q^2/m_H^2, where m_Q is the heavy-quark mass and m_H is the Higgs-boson mass. The calculation contains corrections through next-to-leading order in the strong-coupling constant alpha_s and the square of the heavy-quark velocity v, and includes a resummation of logarithms of m_H^2/m_Q^2 at next-to-leading logarithmic accuracy. We have developed a new method, which makes use of Abel summation, accelerated through the use of Pade approximants, to deal with divergences in the resummed expressions for the quarkonium light-cone distribution amplitudes. This approach allows us to make definitive calculations of the resummation effects. Contributions from the order-alpha_s and order-v^2 corrections to the light-cone distribution amplitudes that we obtain with this new method differ substantially from the corresponding contributions that one obtains from a model light-cone distribution amplitude [M. Koenig and M. Neubert, J. High Energy Phys. 08 (2015) 012]. Our results for the real parts of the direct-process amplitudes are considerably smaller than those from one earlier calculation [G. T. Bodwin, H. S. Chung, J.-H. Ee, J. Lee, and F. Petriello, Phys. Rev. D 90, 113010 (2014)], reducing the sensitivity to the Higgs-boson--heavy-quark couplings, and are somewhat smaller than those from another earlier calculation [M. Koenig and M. Neubert, J. High Energy Phys. 08 (2015) 012]. However, our results for the standard-model Higgs-boson branching fractions are in good agreement with those in M. Koenig and M. Neubert, J. High Energy Phys. 08 (2015) 012.

    hep-phPRD(2017)·43 citations
16. 16*

    Odderon and Pomeron as Fractal Dimension in $pp$ and $\bar{p}p$ Total Cross Sections

    F. S. Borcsik🇧🇷 · S. D. Campos🇧🇷

    In this paper one presents a naive parametrization to $pp$ and $\bar{p}p$ total cross sections. The main goal of this parametrization is to study the possible fractal structure present in the total cross section. The result of the fitting procedure shows two different fractal dimensions: a negative (low-energies) and a positive (high-energies). The negative fractal dimension represents the emptiness of the total cross section structure and the positive represents the filling up process with the energy increase. Hence, the total cross section presents a multifractal behavior. At low-energies, the odderon exchange may be associated with the negative fractal dimension and at high-energies, the pomeron may be associated with the positive fractal dimension. Therefore, the exchange of odderons and pomerons may be viewed as a transition from a less well-defined to a more well-defined internal structure, depending on the energy.

    hep-phMod.Phys.Lett.A(2016)·5 citations
17. 17*

    Atmospheric Neutrinos: Status and Prospects

    Sandhya Choubey🇮🇳

    We present an overview of the current status of neutrino oscillation studies at atmospheric neutrino experiments. While the current data gives some tentalising hints regarding the neutrino mass hierarchy, octant of ${\theta }_{23}$ and ${\delta }_{CP}$, the hints are not statistically significant. We summarise the sensitivity to these sub-dominant three-generation effects from the next-generation proposed atmospheric neutrino experiments. We next present the prospects of new physics searches such as non-standard interactions, sterile neutrinos and CPT violation studies at these experiments.

    hep-phNPB(2016)·10 citations
18. 18*

    Preheating after technicolor inflation

    Phongpichit Channuie (Walailak U.)🇹🇭 · Peeravit Koad (Walailak U.)🇹🇭

    We investigate the particle production due to parametric resonances in model of inflation where the lightest composite state stemming from the minimal walking technicolor theory plays the role of the inflaton. For model of inflation, the effective theory couples non-minimally to gravity. Regarding the preheating, we study in details a model of a composite inflaton field $\varphi$ coupled to another scalar field $\chi$ with the interaction term $g^2{\varphi }^2{\chi }^2$. Particularly, in the Minkowski space, the stage of parametric resonances can be described by the Mathieu equation. Interestingly, we discover that broad resonances can be typically achieved and potentially efficient in our model causing the number of particle density in this process exponentially increases.

    hep-phgr-qchep-thPRD(2016)·9 citations
19. 19*

    Improved Cosmic-Ray Injection Models and the Galactic Center Gamma-Ray Excess

    Eric Carlson🇺🇸 · Tim Linden🇺🇸 · Stefano Profumo🇺🇸

    Fermi-LAT observations of the Galactic Center (GC) have revealed a spherically- symmetric excess of GeV gamma rays extending to at least 10 deg from the dynamical center of the Galaxy. A critical uncertainty in extracting the intensity, spectrum, and morphology of this excess concerns the accuracy of astrophysical diffuse gamma-ray emission models near the GC. Recently, it has been noted that many diffuse emission models utilize a cosmic-ray injection rate far below that predicted based on the observed star formation rate in the Central Molecular Zone. In this study, we add a cosmic-ray injection component which non-linearly traces the Galactic H2 density determined in three-dimensions, and find that the associated gamma-ray emission is degenerate with many properties of the GC gamma-ray excess. In models that utilize a large sideband (40x40 deg surrounding the GC) to normalize the best-fitting diffuse emission models, the intensity of the GC excess decreases by a factor of 2, and the morphology of the excess becomes less peaked and less spherically symmetric. In models which utilize a smaller region of interest (15x15 deg) the addition of an excess template instead suppresses the intensity of the best-fit astrophysical diffuse emission, and the GC excess is rather resilient to changes in the details of the astrophysical diffuse modeling. In both analyses, the addition of a GC excess template still provides a statistically significant improvement to the overall fit to the gamma-ray data. We also implement advective winds at the GC, and find that the Fermi-LAT data strongly prefer outflows of order several hundred km/s, whose role is to efficiently advect low-energy cosmic rays from the Galactic center. Finally, we perform numerous tests of our models, and conclude that they significantly improve our understanding of multi-wavelength non-thermal emission from the GC.

    ↳ astro-ph.HEastro-ph.GAhep-phPRD(2016)·60 citations
20. 20*

    Polyakov loop in 2+1 flavor QCD from low to high temperatures

    A. Bazavov🇺🇸 · N. Brambilla🇩🇪 · H.-T. Ding🇨🇳 · P. Petreczky🇺🇸 · H.-P. Schadler🇺🇸 · A. Vairo🇩🇪 · J. H. Weber🇩🇪

    We study the free energy of a static quark in QCD with 2+1 flavors in a wide temperature region, 116 MeV $<T<$ 5814 MeV, using the highly improved staggered quark (HISQ) action. We analyze the transition region in detail, obtain the entropy of a static quark, show that it peaks at temperatures close to the chiral crossover temperature and also revisit the temperature dependence of the Polyakov loop susceptibilities using gradient flow. We discuss the implications of our findings for the deconfinement and chiral crossover phenomena at physical values of the quark masses. Finally a comparison of the lattice results at high temperatures with the weak-coupling calculations is presented.

    ↳ hep-lathep-phhep-thnucl-thPRD(2016)·147 citations
21. 21*

    Solving functional flow equations with pseudo-spectral methods

    Julia Borchardt🇩🇪 · Benjamin Knorr🇩🇪

    We apply pseudo-spectral methods to integrate functional flow equations with high accuracy, extending earlier work on functional fixed point equations \cite{Borchardt:2015rxa}. The advantages of our method are illustrated with the help of two classes of models: first, to make contact with literature, we investigate flows of the O$(N)$-model in 3 dimensions, for $N=1,4$ and in the large $N$ limit. For the case of a fractal dimension, $d=2.4$, and $N=1$, we follow the flow along a separatrix from a multicritical fixed point to the Wilson-Fisher fixed point over almost 13 orders of magnitude. As a second example, we consider flows of bounded quantum-mechanical potentials, which can be considered as a toy model for Higgs inflation. Such flows pose substantial numerical difficulties, and represent a perfect test bed to exemplify the power of pseudo-spectral methods.

    ↳ hep-thhep-phPRD(2016)·67 citations
22. 22*

    Robust Inflation from Fibrous Strings

    C.P. Burgess🇨🇦 · M. Cicoli🇮🇹 · S. de Alwis🇺🇸 · F. Quevedo🇮🇹

    Successful inflationary models should (i) describe the data well; (ii) arise generically from sensible UV completions; (iii) be insensitive to detailed fine-tunings of parameters and (iv) make interesting new predictions. We argue that a class of models with these properties is characterized by relatively simple potentials with a constant term and negative exponentials. We here continue earlier work exploring UV completions for these models, including the key (though often ignored) issue of modulus stabilisation, to assess the robustness of their predictions. We show that string models where the inflaton is a fibration modulus seem to be robust due to an effective rescaling symmetry, and fairly generic since most known Calabi-Yau manifolds are fibrations. This class of models is characterized by a generic relation between the tensor-to-scalar ratio $r$ and the spectral index $n_s$ of the form $r\propto (n_s-1{)}^2$ where the proportionality constant depends on the nature of the effects used to develop the inflationary potential and the topology of the internal space. In particular we find that the largest values of the tensor-to-scalar ratio that can be obtained by generalizing the original set-up are of order $r\lesssim 0.01$. We contrast this general picture with specific popular models, such as the Starobinsky scenario and $\alpha$-attractors. Finally, we argue the self consistency of large-field inflationary models can strongly constrain non-supersymmetric inflationary mechanisms.

    ↳ hep-thastro-ph.COhep-phJCAP(2016)·90 citations
23. 23*

    The 21 cm signal and the interplay between dark matter annihilations and astrophysical processes

    Laura Lopez-Honorez (Intl. Solvay Inst., Brussels & Vrije U., Brussels)🇧🇪 · Olga Mena (Valencia U., IFIC)🇪🇸 · Ángeles Moliné (Valencia U., IFIC & Lisbon, CFTP)🇪🇸 · Sergio Palomares-Ruiz (Valencia U., IFIC)🇪🇸 · Aaron C. Vincent (IPPP, U. Durham)🇬🇧

    Future dedicated radio interferometers, including HERA and SKA, are very promising tools that aim to study the epoch of reionization and beyond via measurements of the 21 cm signal from neutral hydrogen. Dark matter (DM) annihilations into charged particles change the thermal history of the Universe and, as a consequence, affect the 21 cm signal. Accurately predicting the effect of DM strongly relies on the modeling of annihilations inside halos. In this work, we use up-to-date computations of the energy deposition rates by the products from DM annihilations, a proper treatment of the contribution from DM annihilations in halos, as well as values of the annihilation cross section allowed by the most recent cosmological measurements from the Planck satellite. Given current uncertainties on the description of the astrophysical processes driving the epochs of reionization, X-ray heating and Lyman-$\alpha$ pumping, we find that disentangling DM signatures from purely astrophysical effects, related to early-time star formation processes or late-time galaxy X-ray emissions, will be a challenging task. We conclude that only annihilations of DM particles with masses of $\sim 100$ MeV, could leave an unambiguous imprint on the 21 cm signal and, in particular, on the 21 cm power spectrum. This is in contrast to previous, more optimistic results in the literature, which have claimed that strong signatures might also be present even for much higher DM masses. Additional measurements of the 21 cm signal at different cosmic epochs will be crucial in order to break the strong parameter degeneracies between DM annihilations and astrophysical effects and undoubtedly single out a DM imprint for masses different from $\sim 100$ MeV.

    ↳ astro-ph.COhep-phJCAP(2016)·93 citations
24. 24*

    Ultraviolet divergences in non-renormalizable supersymmetric theories

    A.V. Smilga🇫🇷

    We present a pedagogical review of our current understanding of the ultraviolet structure of N = (1,1) 6D supersymmetric Yang-Mills theory and of N = 8 4D supergravity. These theories are not renormalizable, they involve power ultraviolet divergences and, in all probability, an infinite set of higher-dimensional counterterms that contribute to on-mass-shell scattering amplitudes. A specific feature of supersymmetric theories (especially, of extended supersymmetric theories) is that these counterterms may not be invariant off shell under the full set of supersymmetry transformations. The lowest-dimensional nontrivial counterterm is supersymmetric on shell. Still higher counterterms may lose even the on-shell invariance. On the other hand, the full effective Lagrangian, generating the amplitudes and representing an infinite sum of counterterms, still enjoys the complete symmetry of original theory. We also discuss simple supersymmetric quantum-mechanical models that exhibit the same behaviour.

    ↳ hep-thgr-qchep-phPhys.Part.Nucl.Lett.(2017)·25 citations
25. 25*

    Field Theoretic Approaches To Early Universe

    Sayantan Choudhury🇮🇳

    This thesis compiles the results of six works which deal with - inflationary model building and estimation of cosmological parameters from various field theoretic setup, quantification of reheating temperature, studies of leptogenesis in braneworld and estimation of primordial non-Gaussianity from $\mathcal{N}=1$ supergravity using $\delta N$ formalism. We start our discussion with exploring the possibility of MSSM inflation in the light of recent observed data from various D -flat directions using the saddle and inflection point techniques. The effective inflaton potential around saddle point and inflection point have been utilized in estimating the observable parameters and confronting them with WMAP7 and Planck dataset. Next we explore the possibility of inflation from the five dimensional $\mathcal{N}=2$ supergravity setup by deriving the effective potential in the context of RS like braneworld model and DBI Galileon. After deriving an four dimensional effective potential, we obtain the inflationary observables from both the scenarios and confront them with the WMAP data. Further we fit the CMB angular power spectra from TT anisotropy and other polarization data obtained from WMAP. Further, we discuss the non-trivial features of reheating from supergravity inspired braneworld model, where the results are to some extent different from that of the usual low energy GR counterpart, because of the modified Friedmann equations in this setup. We explicitly derive the analytical expressions for the reheating temperature and further solve the evolution equation of the number density of thermal gravitino which results in the gravitino abundance. Finally, we study the primordial local type of non-Gaussian features using $\delta N$ formalism for a generic class of sub-Planckian models dominated by the Hubble-induced corrections within $\mathcal{N}=1$ supergravity framework.

    ↳ hep-thastro-ph.COgr-qchep-ph12 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.