Experimental data suggest the existence of a minimal length scale in annihilation process for the reaction e+e- --> gamma gamma (gamma). Nonlinear electrodynamics coupled to gravity and satisfying the weak energy condition predicts, for an arbitrary gauge invariant lagrangian, the existence of a spinning charged electromagnetic soliton asymptotically Kerr-Newman for a distant observer with a gyromagnetic ratio g=2. Its internal structure includes an equatorial disk of de Sitter vacuum which has properties of a perfect conductor and ideal diamagnetic, and displays superconducting behavior within a single spinning soliton. De Sitter vacuum supplies a particle with the finite positive electromagnetic mass related to breaking of space-time symmetry. We apply this approach to interpret the existence of a minimal characteristic length scale in annihilation.
We study all tree-level neutralino annihilation processes concerning energy-dependence at the mSUGRA benchmark point SPS1a using tree-level calculators MadGraph and CompHEP as well as FormCalc. We further investigate the total tree-level neutralino annihilation cross section by scanning over the mSUGRA parameters and identifying the dominant channels in every region. The results for the cross sections are presented in the m1/2-m0 planes for different values of tan(beta) and A0. We identify as well the resonances due to the exchange of the heavy Higgs bosons A and H in the s-channel of many neu…
We evaluate the relic density of neutralinos in the minimal supergravity (mSUGRA) model. All 2-->2 neutralino annihilation diagrams, as well as all processes involving sleptons, charginos, neutralinos and third generation squarks are included. Relativistic thermal averaging of the velocity times cross sections is performed. We find that co-annihilation effects are only important on the edges of the model parameter space, where some amount of fine-tuning is necessary to obtain a reasonable relic density. Alternatively, at high tan(beta), annihilation through very broad Higgs resonances gives ri…
We re-examine the stop co-annihilation scenario of the Minimal Supersymmetric Standard Model, wherein a bino-like lightest supersymmetric particle has a thermal relic density set by co-annihilations with a scalar partner of the top quark in the early universe. We concentrate on the case where only the top partner sector is relevant for the cosmology, and other particles are heavy. We discuss the cosmology with focus on low energy parameters and an emphasis on the implications of the measured Higgs boson mass and its properties. We find that the irreducible direct detection signal correlated wi…
The measurements of the total cross section of the $ e^+e^-\toγγ$ reaction from the VENUS, TOPAS, OPAL, DELPHI, ALEPH and L3 collaborations, collected between 1989 to 2003, are used to perform a $ χ^{2} $ test to search for a finite interaction length in direct contact term. The experimental data of the total cross section compared to the QED cross section of a $ χ^{2} $ test allows, to set limit on a finite interaction length $ r_{e}=(1.25\pm 0.16) \times 10 ^{-17} [cm] $. In the direct contact term annihilation is this interaction lengths a measure for the size of the electron.
Weak corrections to Minimal Dark Matter annihilations
INFN Sezione di Pisa, Italia（意大利国家核物理研究所比萨分部）；Dipartimento di Fisica dell’Università di Pisa, Italia（意大利比萨大学物理系）；Departamento de Física Teórica and Instituto de Física Teórica, Universidad Autónoma de Madrid, Spain（西班牙马德里自治大学理论物理系及理论物理研究所）
We investigate monoenergetic gamma-ray signatures from annihilations of dark matter comprised of Z^1, the first Kaluza-Klein excitation of the Z boson, in a non-minimal Universal Extra Dimensions model. The self-interactions of the non-Abelian Z^1 gauge boson give rise to a large number of contributing Feynman diagrams that do not exist for annihilations of the Abelian gauge boson B^1, which is the standard Kaluza-Klein dark matter candidate. We find that the annihilation rate is indeed considerably larger for the Z^1 than for the B^1. Even though relic density calculations indicate that the m…
Minimal scalar Higgs portal dark matter model is increasingly in tension with recent results form direct detection experiments like LUX and XENON. In this paper we make a systematic study of minimal extension of the $ \mathbb{Z}_2$ stabilised singlet scalar Higgs portal scenario in terms of their prospects at direct detection experiments. We consider both enlarging the stabilising symmetry to $\mathbb{Z}_3$ and incorporating multipartite features in the dark sector. We demonstrate that in these non-minimal models the interplay of annihilation, co-annihilation and semi-annihilation processes co…
We study the dark matter from an inert doublet and a complex scalar singlet stabilized by $\mathbb{Z}_N$ symmetries. This field content is the minimal one that allows dimensionless semi-annihilation couplings for $N > 2$. We consider explicitly the $\mathbb{Z}_3$ and $\mathbb{Z}_4$ cases and take into account constraints from perturbativity, unitarity, vacuum stability, necessity for the electroweak $\mathbb{Z}_N$ preserving vacuum to be the global minimum, electroweak precision tests, upper limits from direct detection and properties of the Higgs boson. Co-annihilation and semi-annihilation o…
We evaluate the relic density of neutralinos in the minimal supergravity (mSUGRA) model. All 2->2 neutralino annihilation diagrams, as well as all initial states involving sleptons, charginos, neutralinos and third generation squarks are included. Relativistic thermal averaging of the velocity times cross sections is performed. We find that co-annihilation effects are only important on the edges of the model parameter space, where some amount of fine-tuning is necessary to obtain a reasonable relic density. Alternatively, at high tan(beta), annihilation through the broad Higgs resonances gives…
We consider the resummation of large electroweak Sudakov logarithms for the annihilation of neutralino DM with $\mathcal{O}$(TeV) mass to high-energy photons in the minimal supersymmetric standard model, extending previous work on the minimal wino and Higgsino models. We find that NLL resummation reduces the yield of photons by about $20\%$ for Higgsino-dominated DM at masses around 1~TeV, and up to $45\%$ for neutralinos with larger wino admixture at heavier masses near 3~TeV. This sizable effect is relevant when observations or exclusion limits are translated into MSSM parameter-space constr…
We take a closer look at the gaugino masses in the context of pure gravity mediation models/minimal split SUSY models. We see that the gaugino mass spectrum has a richer structure in the presence of vector-like matter fields even when they couple to the supersymmetry breaking sector only through Planck suppressed operators. For example, the gluino mass can be much lighter than in anomaly mediation, enhancing the detectability of the gluino at the LHC experiments. The rich gaugino spectrum also allows new possibilities for dark matter scenarios such as the bino-wino co-annihilation, bino-gluino…
It has been proposed that the incorporation of an observer independent minimal length scale into the quantum field theories of the standard model effectively describes phenomenological aspects of quantum gravity. The aim of this paper is to interpret this description and its implications for scattering processes.
We consider the modification to Kruglov's non-linear electrodynamics in the presence of minimal length ($l_p$), by considering a specific formulation of generalized uncertainty principle (GUP). The presence of minimal length has been motivated by several candidate theories of quantum-gravity (both perturbative and non-perturbative). We show that, such minimal length modifications could lead to momentum dependent bounds on zero-point electric field strength, for the aforementioned non-linear model of electrodynamics. We further show that, the existence of minimal length modifies the measure of …
We study precise calculation of neutralino relic density in the minimal supergravity model. We compare the exact formula for the thermal average of the neutralino annihilation cross section times relative velocity with the expansion formula in terms of the temperature, including all the contributions to neutralino annihilation cross section analytically. We confirm that the expansion formula fails badly near s-channel poles. We show that the expansion method causes 5-10 % error even far away from the poles.
An excess in gamma-rays emanating from the galactic centre has recently been observed in the Fermi-LAT data. This signal can be interpreted as resulting from WIMP annihilation, with the spectrum well-fit by dark matter annihilating dominantly into either bottom-quark or Higgs pairs. Supersymmetric models provide a well-motivated framework to study the implications of this signal in these channels. With a neutralino dark matter candidate, the gamma-ray excess cannot be easily accommodated in the minimal supersymmetric model, which in any case requires tuning below the percent level to explain t…
Semi-annihilation is a generic feature of dark matter theories with symmetries larger than Z2. We investigate two examples with multi-component dark sectors comprised of an SU(2)L singlet or triplet fermion besides a scalar singlet. These are respectively the minimal fermionic semi-annihilating model, and the minimal case for a gauge-charged fermion. We study the relevant dark matter phenomenology, including the interplay of semi-annihilation and the Sommerfeld effect. We demonstrate that semi-annihilation in the singlet model can explain the gamma ray excess from the galactic center. For the …
We present the energy spectra of the fluxes of positrons, anti-protons and photons generated by Dark Matter annihilations in our galaxy, as univocally predicted by the model of Minimal Dark Matter. Due to multi-TeV masses and to the Sommerfeld enhancement of the annihilation cross section, distinctive signals are generated above the background, even with a modest astrophysical boost factor, in the range of energies soon to be explored by cosmic ray experiments.
We revisit the annihilation of dark matter to neutrinos in the Sun near the WW and tt kinematic thresholds. We investigate the potential importance of annihilation to WW* in a minimal dark matter model in which a Majorana singlet is mixed with a vector-like electroweak doublet, but many results generalize to other models of weakly-interacting dark matter. We re-evaluate the indirect detection constraints on this model and find that, once all annihilation channels are properly taken into account, the most stringent constraints on spin-dependent scattering for dark matter mass 60 GeV < mX < mt a…
We show how a difference in the correlation length longitudinally and transversely, with respect to the jet axis in e+e- annihilation, arises naturally in a model for Bose-Einstein correlations based on the Lund string model. The difference is more apparent in genuine three-particle correlations and they are therfore a good probe for the longitudinal stretching of the string field.
We calculate the QCD corrections to the cross section of e^+ e^- -> t anti-b H^- and its charge-conjugate counterpart within the minimal supersymmetric extension of the Standard Model. This process is particularly important if m_t < m_H + m_b and root(s) < 2 m_H, so that t -> b H^+ and e^+ e^- -> H^+ H^- are not allowed kinematically. Large logarithmic corrections that arise in the on-mass-shell scheme of quark mass renormalization, especially from the t anti-b H^- Yukawa coupling for large values of tan(beta), are resummed by adopting the modified minimal-subtraction scheme, so that the conve…
Generalized uncertainty relations are known to provide a minimal length $\hbar\sqrtβ$. The effect of such minimal length in the Casimir-Polder interactions between neutral atoms (molecules) is studied. The first order correction term in the minimal uncertainty parameter is derived and found to describe an attractive potential scaling as $r^{-9}$ as opposed to the well known $r^{-7}$ long range retarded potential.
Phenomenological studies of quantum gravity have proposed a modification of the commutator between position and momentum in quantum mechanics so to introduce a minimal uncertainty in position in quantum mechanics. Such a minimal uncertainty and the consequent minimal measurable length have important consequences on the dynamics of quantum systems. In the present work, we show that such consequences go beyond dynamics, reaching the definition of quantities such as energy, momentum, and the same Hamiltonian. Furthermore, since the Hamiltonian, defined as the generator of time evolution, results …
For the minimal wino and Higgsino benchmark models we provide accurate energy spectra of high-energy photons from TeV scale dark-matter annihilation $χχ\to γ+X$ by merging electroweak Sudakov resummation near maximal energy with the electroweak parton-shower PPPC4DM, and accounting for the Sommerfeld effect. Electroweak resummation significantly changes the shape of the photon-energy spectrum in the wide range $E_γ\sim (0.6\ldots 1)\, m_χ$ and hence the form of the so-called "line-signal".
A detailed study of a fermionic quintuplet dark matter in a left-right symmetric scenario is performed in this article. The minimal quintuplet dark matter model is highly constrained from the WMAP dark matter relic density (RD) data. To elevate this constraint, an extra singlet scalar is introduced. It introduces a host of new annihilation and co-annihilation channels for the dark matter, allowing even sub-TeV masses. The phenomenology of this singlet scalar is studied in detail in the context of the Large Hadron Collider (LHC) experiment. The production and decay of this singlet scalar at the…
The branching ratio for the rare two-body B_s -> rho gamma decay is calculated using the factorization assumption. This transition is dominated by the annihilation diagrams and, in principle, prone to receiving substantial contributions from new physics. We estimate Br(B_s -> rho gamma) = 1.6 x 10^-9 within the Standard Model and investigate the sensitivity of this decay mode to the effects of two new physics scenarios: vector quark model and supersymmetry. Our results indicate that the shift in branching ratio is at most around 10% with the addition of vector quarks and is negligibly small in…
A momentum representation treatment of the hydrogen atom problem with a generalized uncertainty relation,which leads to a minimal length (ΔX_{i})_{min}= \hbar \sqrt(3β+β'), is presented. We show that the distance squared operator can be factorized in the case β'=2β. We analytically solve the s-wave bound-state equation. The leading correction to the energy spectrum caused by the minimal length depends on \sqrtβ. An upper bound for the minimal length is found to be about 10^{-9} fm.
We perform a study of the dark matter candidates of a constrained version of the minimal R-parity-conserving supersymmetric model with a gauged $U(1)_{B-L}$. It turns out that there are four additional candidates for dark matter in comparison to the MSSM: two kinds of neutralino, which either correspond to the gaugino of the $U(1)_{B-L}$ or to a fermionic bilepton, as well as "right-handed" CP-even and -odd sneutrinos. The correct dark matter relic density of the neutralinos can be obtained due to different mechanisms including new co-annihilation regions and resonances. The large additional Y…
High resolution simulations reveal that in the cold dark matter scenario the structures form hierarchically and a large number of substructures survive in the galactic halos. The substructures can be probed if they emit gamma rays via dark matter annihilation. We calculated the gamma ray fluxes from the dark matter annihilations in the substructures of our Galaxy within the frame of the minimal supersymmetric extension of the standard model. The uncertainties of the prediction from both the low energy supersymmetry and especially from the density profiles of dark matter in the substructures ar…
The Fermi Gamma-ray Space Telescope discovered two γ-ray emitting bubble-shaped structures that extend nearly symmetrically on either side of our Galaxy and appear morphologically connected to the Galactic center. The origin of the emission is still not entirely clear. It was recently shown that the spectral shape of the emission from the Fermi bubbles is well described by an approximately 50 GeV dark matter particle annihilating to b \bar b, with a normalization corresponding to a velocity average annihilation cross section of < σ_b v > ~ 8 \times 10^{-27} cm^3/s. We study the minimal hidden …
Motivated by the interpretation of the recent results on the TeV gamma radiation from the Galactic center, including the new 2004 HESS data, as a by-product of dark matter particles annihilations, we address the question of the largest possible neutralino masses and pair annihilation cross sections in supersymmetric models. Extending the parameter space of minimal models, such as the mSUGRA and the mAMSB scenarios, to general soft SUSY breaking Higgs masses gives access to the largest possible pair annihilation rates, corresponding to resonantly annihilating neutralinos with maximal gaugino-hi…
We present the results of a new evaluation of the running fine structure constant $α$ at the scale of the $Z$ mass in which the role of the $e^+e^-$ annihilation input data needed in this evaluation is minimized. This is achieved by reducing the weight function $M_Z^2/(s(M_Z^2-s))$ in the dispersion integral over the $e^+e^-$ annihilation data by subtracting a polynomial function from the weight function which mimics its energy dependence in given energy intervals. In order to compensate for this subtraction the same polynomial weight integral is added again but is now evaluated on a circular …
Modifications of the gyromagnetic moment of electrons and muons due to a minimal length scale combined with a modified fundamental scale M_f are explored. Deviations from the theoretical Standard Model value for g-2 are derived. Constraints for the fundamental scale M_f are given.
Theories of quantum gravity suggest the existence of a minimal length scale. We study the consequences of a particular implementation of the idea of a minimal length scale in the model of large extra dimensions, the ADD model. To do this we have looked at real graviton production in association with a jet at hadron colliders. In the minimal length scenario, the bounds on the effective string scale are significantly less stringent than those derived in the conventional ADD model, both at the upgraded Tevatron and at the Large Hadron Collider.
The CACTUS experiment recently observed a gamma ray excess above 50 GeV from the direction of the Draco dwarf spheroidal galaxy. Considering that Draco is dark matter dominated the gamma rays may be generated through dark matter annihilation in the Draco halo. In the framework of the minimal supersymmetric extension of the standard model we explore the parameter space to account for the gamma ray signals at CACTUS. We find that the neutralino mass is constrained to be approximately in the range between 100 GeV ~ 400 GeV and a sharp central cuspy of the dark halo profile in Draco is necessary t…
We study the spectra of gamma ray signals that arise from dark matter annihilation in the universe. We focus on the large class of theories where the photon spectrum includes both continuum spectrum of gamma rays that arise from annihilation into Standard Model states at tree level, as well as monochromatic gamma rays arising from annihilation directly into two photons at the one loop level. In this class of theories we obtain lower bounds on the ratio of the strength of the gamma ray line relative to the gamma ray continuum as a function of the dark matter mass and spin. These limits are obta…
