Can the morphology of γ-ray emission distinguish annihilating from decaying dark matter?

Recent results from the PAMELA, ATIC, FERMI and HESS experiments have focused attention on the possible existence of high energy cosmic rays e+ e- that may originate from dark matter annihilations or decays in the Milky Way. Here we examine the morphology of the associated γ-ray emission after propagation of the electrons generated by both annihilating and decaying dark matter models. We focus on photon energies of 1, 10, and 50 GeV (relevant for the FERMI satellite) and consider different propagation parameters. Our main conclusion is that distinguishing annihilating from decaying dark matter may only be possible if the propagation parameters correspond to the most optimistic diffusion models. In addition, we point to examples where morphology can lead to an erroneous interpretation of the source injection energy.     

Constraints on light dark matter from core-collapse supernovae

We show that light (approximately or = 1-30 MeV) dark matter particles can play a significant role in core-collapse supernovae, if they have relatively large annihilation and scattering cross sections, as compared to neutrinos. We find that if such particles are lighter than approximately or = 10 MeV and reproduce the observed dark matter relic density, supernovae would cool on a much longer time scale and would emit neutrinos with significantly smaller energies than in the standard scenario, in disagreement with observations. This constraint may be avoided, however, in certain situations for which the neutrino-dark-matter scattering cross sections remain comparatively small.     

Experimental investigation of deuteron photodisintegration in the δ-resonance region

Differential cross sections for the deuteron photodisintegration process were measured for photon energies between 200 and 440 MeV using the tagged photon beam facility of the Bonn 500 MeV synchrotron. At eight angles between 18° and 145° charged particles were detected simultaneously in time-of-flight spectrometers consisting of scintillation counters. Above the resonance region the measured cross sections agree fairly well with earlier results, whereas there are larger discrepancies at low photon energies.     

Search for pair-produced neutralinos in events with photons and missing energy from e+e- collisions at ?s = 130 - 183\sqrt s = 130 - 183 GeV

The events with two photons and missing (transverse) energy collected by the DELPHI detector at centre-of-mass energies between 130 GeV and 183 GeV have been studied to search for processes of the type e⁺e^- → YY with the subsequent decay Y → X7, where X is an undetectable neutral particle. Reactions of this kind are expected in supersymmetric models, where the Y particle can be either the lightest neutralino, decaying to a photon and a gravitino, or the next-to-lightest neutralino, decaying to a photon and the lightest neutralino. To study the case of long-lived Y particles, a search for single-photon events with the reconstructed photon axis pointing far from the beam interaction region has also been performed. No evidence for a deviation from Standard Model expectations has been observed in the data and upper limits have been derived on the signal cross-section as a function of the the X and Y masses and of the Y mean decay path.     

Constraints from the Wilkinson microwave anisotropy probe on decaying cold dark matter

We reformulate cosmological perturbations in the decaying cold dark matter model, and calculate cosmological microwave background anisotropies. By comparing our predictions with data from the Wilkinson Microwave Anisotropy Probe, we derive a new bound on the abundance and lifetime of decaying dark matter particles. The lifetime is constrained to Gamma(- 1)> or =123 Gyr at 68% C.L. (52 Gyr at 95.4% C.L.) when cold dark matter consists only of such decaying particles. We also consider a more general case and show that the constraint generalizes to Omega(DDM )h2 less, similar -0.5(Gamma (-1)/1 Gyr) (-1)+0.12 for Gamma(- 1)> or =5 Gyr at 95.4% C.L.     

Indications of a four-quark structure for the X(3872) and X(3876) particles from recent Belle and BABAR data

Recent results by Belle and BABAR point to the existence of a second X particle decaying in D(0)D(0)pi(0), a few MeV above the X(3872). We identify the two X states with the neutral particles predicted by the four-quark model and show that production and decays are consistent with this assignment. We consider the yet-to-be-observed charged partners and give new hints on how to look for them.     

Possible evidence for MeV dark matter in dwarf spheroidals

The observed 511 keV emission from the galactic bulge could be due to very light (MeV) annihilating dark matter particles. To distinguish this hypothesis from conventional astrophysical sources, we study dwarf spheroidals in the region observed by the International Gamma-Ray Astrophysics Laboratory/SPI such as Sagittarius. As these galaxies have comparatively few stars, the prospects for 511 keV emission from standard astrophysical scenarios are minimal. The dwarf spheroidals do, however, contain copious amounts of dark matter. The observation of 511 keV emission from Sagittarius should be a "smoking gun" for MeV dark matter.     

DEPFET detectors for direct detection of MeV Dark Matter particles

The existence of dark matter is undisputed, while the nature of it is still unknown. Explaining dark matter with the existence of a new unobserved particle is among the most promising possible solutions. Recently dark matter candidates in the MeV mass region received more and more interest. In comparison to the mass region between a few GeV to several TeV, this region is experimentally largely unexplored. We discuss the application of a RNDR DEPFET semiconductor detector for direct searches for dark matter in the MeV mass region. We present the working principle of the RNDR DEPFET devices and review the performance obtained by previously performed prototype measurements. The future potential of the technology as dark matter detector is discussed and the sensitivity for MeV dark matter detection with RNDR DEPFET sensors is presented. Under the assumption of six background events in the region of interest and an exposure of 1 kg year a sensitivity of about \(\overline{\sigma }_{e} = 10^{-41}\,{\mathrm {cm}}^2\) for dark matter particles with a mass of 10 MeV can be reached.     

Extending the MSSM with Singlet Higgs and Right Handed Neutrino for the Self-Interacting Dark Matter

In order to meet the requirement of BBN,the right handed neutrino is added to the singlet Higgs sector in the GNMSSM.The spectrum and Feynman rules are calculated.the dark matter pheonomenology is also studied.In case of λ ~ 0,the singlet sector can give perfect explanation of relic abundance of dark matter and small cosmological structure simulations.The BBN constraints on the light mediator can be easily solved by decaying to the right handed neutrino.When the λ_N is at the order of O(0.1),the mass of the mediator can be constrained to several MeV.     

Terrestrial gamma-ray flashes as powerful particle accelerators

Strong electric discharges associated with thunderstorms can produce terrestrial gamma-ray flashes (TGFs), i.e., intense bursts of x?rays and γ?rays lasting a few milliseconds or less. We present in this Letter new TGF timing and spectral data based on the observations of the Italian Space Agency AGILE satellite. We determine that the TGF emission above 10 MeV has a significant power-law spectral component reaching energies up to 100 MeV. These results challenge TGF theoretical models based on runaway electron acceleration. The TGF discharge electric field accelerates particles over the large distances for which maximal voltages of hundreds of megavolts can be established. The combination of huge potentials and large electric fields in TGFs can efficiently accelerate particles in large numbers, and we reconsider here the photon spectrum and the neutron production by photonuclear reactions in the atmosphere.     

WHAT IS THE NATURE OF THE NEWLY DISCOVERED HEAVY PARTICLE γ(9.5)

In this paper, we discuss the nature of the newly discovered heavy particle Y（9.5）. Five possibilities of experimental criteria are analysed. We show that if Y is a heavy photon, an intermediate boson, a bound state of straton-antistraton or a hadron without valence stratons, and all the Γee will differ by several orders of magnitude and can therefore be discriminated easily in e⁺ e^-collision experiments. The width value Fee and its ratio of γ to γ' are not identical for the case of colour excited states of meson and the case of bound states of the new straton-antistraton. The masses of other existing new particles can also be predicted. In particular, the masses of weakly decaying heavy particles are not the same for these two cases, which may be regarded as a criterion to discriminate between these two cases. We have also discussed the main decaying properties of γ for these five possibilities.     

Measurement of the two-body photodisintegration of3He in theΔ(1236) resonance region

The³He(γ, p)d reaction has been measured in the photon energy region between 200 MeV and 450 MeV at proton c.m. angles between 20° and 150°. Protons and deuterons were detected in coincidence with two time-of-flight spectrometers consisting of scintillation counters; both particles were identified and their energies and angles were measured. The angular distributions show a strong forward peak. The differential cross sections fall off with increasing photon energy without showing a significant influence of theΔ resonance.     

Light-particle heavy-ion correlations in deep inelastic processes: A theoretical study of hot-spot particle emission

Using the concept of a “hot spot”, i.e. a space-time localized excitation in the nucleus which subsequently decays via diffusion of heat in nuclear matter, we formulate a model for the emission of light particles in deep-inelastic heavy ion collisions. In-plane angular and energy correlations between n, p, ³He and α-particles and the strongly damped projectile emerging from the reaction 96 MeV ¹⁶O+⁵⁸Ni are calculated as an example. The particle spectra are obtained from classical three-body trajectory calculations with time-dependent initial conditions as given by the non-isotropic temperature field of the hot spot. We are particularly concerned with correlations introduced by the decaying hot spot, by the intrinsic rotation of the emitter, and by the focussing effect of the Coulomb fields of the separating projectile and target residues.     

Non-thermal dark matter,high energy cosmic rays and late-decaying particles from inflationary quantum fluctuations

It has been suggested that the origin of cosmic rays above the GZK limit might be explained by the decay of particles, X, with mass of the order of 10¹² GeV. Generation of heavy particles from inflationary quantum fluctuations is a prime candidate for the origin of the decaying X particles. It has also been suggested that the problem of non-singular galactic halos might be explained if dark matter originates non-thermally from the decay of particles, Y, such that there is a free-streaming length of the order of 0.1 Mpc. Here we explore the possibility that quantum fluctuations might account for the Y particles as well as the X particles. For the case of non-thermal WIMP dark matter with unsuppressed weak interactions we find that there is a general problem with deuterium photo-dissociation, disfavouring WIMP dark matter candidates. For the case of more general dark matter particles, which may have little or no interaction with conventional matter, we discuss the conditions under which X and Y scalars or fermions can account for non-thermal dark matter and cosmic rays. For the case where X and Y scalars are simultaneously produced, we show that galactic halos are likely to have a dynamically significant component of X scalar cold dark matter in addition to the dominant non-thermal dark matter component.     

The new interaction suggested by the anomalous $$^$$Be transition sets a rigorous constraint on the mass range of dark matter

The WIMPs are considered to belong to the favorable dark matter (DM) candidates, but the upper bounds on the interactions between DM and standard model (SM) particles obtained by the upgraded facilities of DM direct detection get lower and lower. Researchers turn their attention to the search for less massive DM candidates, i.e. light dark matter of the MeV scale. The recently measured anomalous transition in \(^8\)Be suggests that there exists a vectorial boson which may mediate the interaction between DM and SM particles. Based on this scenario, we combine the relevant cosmological data to constrain the mass range of DM, and we have found that there exists a model parameter space where the requirements are satisfied, a range of \(10.4 \lesssim m_{\phi } \lesssim \) 16.7 MeV for scalar DM, and \(13.6 \lesssim m_{V} \lesssim 16.7\) MeV for vectorial DM is demanded. Then a possibility of directly detecting such light DM particles via DM–electron scattering is briefly studied in this framework.     

ICPAQGP2001: Conference summary

I review recent progress in ultrarelativistic nucleus-nucleus collisions, and the connection of this field to modern QCD theory of deconfinement and/or chiral symmetry restoration. The talks at this Conference have shown a convergence of data and theory as far as the CERN SPS investigations at √s = 17 GeV are concerned; the parton-hadron phase boundary seems now located atT = 170 ± 10 MeV. New data from RHIC and direct photon production results from CERN have been shown that point out the field’s future direction: analysis of partonic matter atT > 200 MeV. Astrophysics analysis was shown to be linked crucially to further theoretical progress with non-perturbative QCD.     

Fine structure in the208Pb(γ,n) cross section

The total photoneutron cross section of²⁰⁸Pb was measured between 8 and 13 MeV using the bremsstrahlung photon facility from a 35 MeV linac. Considerable resonance structure was observed in the cross section, of which the peak around 9 MeV, as well as the structure around 10.8 MeV may be due toE2 excitations.     

Sensitivity for detection of decay of dark matter particle using ICAL at INO

We report on the simulation studies addressing the possibility of dark matter particle (DMP) decaying into μ⁺μ^? channel. While not much is known about the properties of dark matter particles except through their gravitational effect, it has been recently conjectured that the so-called ‘anomalous Kolar events’ observed some decades ago may be due to the decay of unstable dark matter particles. The aim of this study is to see if this conjecture can be verified at the proposed iron calorimeter (ICAL) detector at INO. We study the possible decay to μ^± mode which may be seen in this detector with some modifications. For the purposes of simulation, we assume that the channel saturates the decay width for the mass ranging from 1 to 50 GeV/c². The aim is not only to investigate the decay signatures, but also, more generally, to establish lower bounds on the lifetime of DMP even if no such decay takes place.     

Proton-antiproton states in high energy photoproduction

Exclusive and inclusive $\text{p}\text{p}$ photoproduction (with ? 2 accompanying charged particles) have been measured in the photon energy range 44–70 GeV. The exclusive process shows no prominent features; the inclusive process shows evidence for S(1936) production as a resonant-like structure with mass 1930 ± 2 MeV and width 12 ± 7 MeV.     

Searching for decaying axionlike dark matter from clusters of galaxies

We constrain the lifetime of radiatively decaying dark matter in clusters of galaxies inspired by generic Kaluza-Klein axions, which have been invoked as a possible explanation for the solar coronal x-ray emission. These particles can be produced inside stars and remain confined by the gravitational potential of clusters. By analyzing x-ray observations of merging clusters, where gravitational lensing observations have identified massive, baryon poor structures, we derive the first cosmological lifetime constraint on this kind of particles of tau > or = 10(23) sec.