Model Independent Signature Research Articles

Dark Matter with DAMA/LIBRA and its perspectives

The existence of Dark Matter particles as a significant portion of the Universe’s total mass is suggested by theoretical reasoning at the galactic and larger scales as well as experimental data. This motivates the DAMA experiment’s efforts to investigate the presence of the Dark Matter particles in the galactic halo by utilizing a model-independent signature with an extremely radio-pure set-up underground. The long-standing, model-independent annual modulation effect at Gran Sasso seen by DAMA with several experimental set-ups is summarized in this paper, along with its perspectives. DAMA/LIBRA-phase2 set-up, ≃ 250 kg highly radio-pure NaI(Tl) further confirms the evidence of a signal that meets all the requirements of the model independent Dark Matter annual modulation signature at high C.L.; the combined exposure of DAMA/NaI and DAMA/LIBRA is 2.86 ton × yr over 22 independent annual cycles. The experiment is currently collecting data in the DAMA/LIBRA–phase2 empowered configuration with an even lower software energy threshold.

Dark matter investigation with DAMA set-ups

Experimental observations and theoretical arguments at Galaxy and larger scales suggested that a large fraction of the universe is composed by Dark Matter particles. This motivated the DAMA experimental efforts to investigate the presence of such particles in the galactic halo by exploiting a model-independent signature and very highly radiopure set-ups deep underground. Here, a review of the model-independent positive results, obtained by the DAMA set-ups at the Gran Sasso National Laboratory of the INFN, and some of the implications will be given.

Primordial gravitational waves spectrum in the Coupled-Scalar-Tachyon Bounce Universe

We extend our study on the Coupled-Scalar-Tachyon Bounce Universe to obtain its gravitational waves spectrum. We derive in detail the equations of motion for the tensorial modes of primordial metric perturbations in the Coupled-Scalar-Tachyon Bounce Universe. We solve for the gravitational wave equations in the pre-bounce contraction and the post-bounce expansion epochs. To match the solutions of the tensor perturbations, we idealise the bounce process yet retaining the essential physical properties of the bounce universe. We put forward two matching conditions: one ensures the continuity of the gravitational wave functions and the other respects the symmetric nature of the bounce dynamics. The matching conditions connect the two independent modes of gravitational waves solutions before and after the bounce. We further analyze the scale dependence and time dependence of the gravitational waves spectra in the bounce universe and compare them with the primordial spectrum in the single field inflation scenario. We discuss the implications to early universe physics and present model independent observational signatures extracted from the bounce universe.

Critical analysis of recent results on electron and positron elastic scattering on proton

Recent data on the cross section ratio for electron and positron elastic scattering on protons are discussed. A deviation from unity of this ratio constitutes a model independent signature of charge-odd contributions that arise from mechanisms beyond the one-photon approximation, as the exchange of two photons. The relevance of this issue is related to that fact that the information on the proton structure from lepton elastic (and inelastic) scattering holds only within a formalism based on the one photon exchange approximation. The present analysis shows that the deviations of the data from unity and from a previously developed theoretical approach lie within the theoretical and experimental errors. The data suggest that other reasons for explanation of the discrepancy between the electromagnetic proton form factors extracted from the experiments according to the polarized and the unpolarized methods are more likely.

Constraining the mass of dark photons and axion-like particles through black-hole superradiance

Ultralight bosons and axion-like particles appear naturally in different scenarios and could solve some long-standing puzzles. Their detection is challenging, and all direct methods hinge on unknown couplings to the Standard Model of particle physics. However, the universal coupling to gravity provides model-independent signatures for these fields. We explore here the superradiant instability of spinning black holes triggered in the presence of such fields. The instability taps angular momentum from and limits the maximum spin of astrophysical black holes. We compute, for the first time, the spectrum of the most unstable modes of a massive vector (Proca) field for generic black-hole spin and Proca mass. The observed stability of the inner disk of stellar-mass black holes can be used to derive direct constraints on the mass of dark photons in the mass range 10−13 eV≲ mV ≲ 3× 10−12 eV. By including also higher azimuthal modes, similar constraints apply to axion-like particles in the mass range 6×10−13 eV≲ mALP ≲ 10−11 eV. Likewise, mass and spin distributions of supermassive BHs—as measured through continuum fitting, Kα iron line, or with the future space-based gravitational-wave detector LISA – imply indirect bounds in the mass range approximately 10−19 eV≲ mV, mALP ≲ 10−13 eV, for both axion-like particles and dark photons. Overall, superradiance allows to explore a region of approximately 8 orders of magnitude in the mass of ultralight bosons.

Nuclear deformation in the laboratory frame

We develop a formalism for calculating the distribution of the axial quadrupole operator in the laboratory frame within the rotationally invariant framework of the configuration-interaction shell model. The calculation is carried out using a finite-temperature auxiliary-field quantum Monte Carlo method. We apply this formalism to isotope chains of even-mass samarium and neodymium nuclei, and show that the quadrupole distribution provides a model-independent signature of nuclear deformation. Two technical advances are described that greatly facilitate the calculations. The first is to exploit the rotational invariance of the underlying Hamiltonian to reduce the statistical fluctuations in the Monte Carlo calculations. The second is to determine quadruple invariants from the distribution of the axial quadrupole operator. This allows us to extract effective values of the intrinsic quadrupole shape parameters without invoking an intrinsic frame or a mean-field approximation.

Dark Kinetic Heating of Neutron Stars and an Infrared Window on WIMPs, SIMPs, and Pure Higgsinos.

We identify a largely model-independent signature of dark matter (DM) interactions with nucleons and electrons. DM in the local galactic halo, gravitationally accelerated to over half the speed of light, scatters against and deposits kinetic energy into neutron stars, heating them to infrared blackbody temperatures. The resulting radiation could potentially be detected by the James Webb Space Telescope, the Thirty Meter Telescope, or the European Extremely Large Telescope. This mechanism also produces optical emission from neutron stars in the galactic bulge, and x-ray emission near the galactic center because dark matter is denser in these regions. For GeV-PeV mass dark matter, dark kinetic heating would initially unmask any spin-independent or spin-dependent dark matter-nucleon cross sections exceeding 2×10^{-45} cm^{2}, with improved sensitivity after more telescope exposure. For lighter-than-GeV dark matter, cross-section sensitivity scales inversely with dark matter mass because of Pauli blocking; for heavier-than-PeV dark matter, it scales linearly with mass as a result of needing multiple scatters for capture. Future observations of dark sector-warmed neutron stars could determine whether dark matter annihilates in or only kinetically heats neutron stars. Because inelastic interstate transitions of up to a few GeV would occur in relativistic scattering against nucleons, elusive inelastic dark matter like pure Higgsinos can also be discovered.

DAMA/LIBRA–phase1 model independent results

Experimental observations and theoretical arguments at Galaxy and larger scales have suggested that a large fraction of the Universe is composed by Dark Matter (DM) particles. This has motivated the DAMA experimental efforts to investigate the presence of such particles in the galactic halo by exploiting a model independent signature with highly radiopure setups deep underground. In this paper, a review of the results obtained with the total exposure of 1.04 ton × yr collected by DAMA/LIBRA–phase1 deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN during seven annual cycles is given. The DAMA/LIBRA–phase1 data give evidence for the presence of DM particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radiopure NaI(Tl) target, at 7.5[Formula: see text] C.L. Including also the data of the first generation DAMA/NaI experiment (cumulative exposure 1.33 ton × yr, corresponding to 14 annual cycles), the C.L. is 9.3[Formula: see text] and the modulation amplitude of the single-hit scintillation events in the (2–6) keV energy interval is: (0.0112 ± 0.0012) cpd/kg/keV; the measured phase is (144 ± 7) days and the measured period is (0.998 ± 0.002) yr, values well in agreement with those expected for DM particles. No systematic or side reaction able to mimic the exploited DM signature has been found or suggested by anyone over more than a decade.

Nuclear deformation at finite temperature.

Deformation, a key concept in our understanding of heavy nuclei, is based on a mean-field description that breaks the rotational invariance of the nuclear many-body Hamiltonian. We present a method to analyze nuclear deformations at finite temperature in a framework that preserves rotational invariance. The auxiliary-field Monte Carlo method is used to generate a statistical ensemble and calculate the probability distribution associated with the quadrupole operator. Applying the technique to nuclei in the rare-earth region, we identify model-independent signatures of deformation and find that deformation effects persist to temperatures higher than the spherical-to-deformed shape phase-transition temperature of mean-field theory.

Bounds on dark matter interpretation of Fermi-LAT GeV excess

Annihilation of light dark matter of mDM≈(10–40) GeV into the Standard Model fermions has been suggested as a possible origin of the gamma-ray excess at GeV energies in the Fermi-LAT data. In this paper, we examine possible model-independent signatures of such dark matter models in other experiments such as AMS-02, colliders, and cosmic microwave background (CMB) measurements. We point out that first generation of fermion final states is disfavored by the existing experimental data. Currently AMS-02 positron measurements provide stringent bounds on cross sections of dark matter annihilation into leptonic final states, and e+e− final state is in severe tension with this constraint, if not ruled out. The e+e− channel will be complementarily verified in an early stage of ILC and future CMB measurements. Light quark final states (qq¯) are relatively strongly constrained by the LHC and dark matter direct detection experiments even though these bounds are model-dependent. Dark matter signals from annihilations into qq¯ channels would be constrained by AMS-02 antiproton data which will be released in very near future. In optimistic case, diffuse radio emission from nearby galaxy (clusters) and the galactic center might provide another hint or limit on dark matter annihilation.

Direct dark matter investigation

Experimental efforts and theoretical developments support that most of the Universe is dark and a large fraction of it should be made of relic particles; many possibilities are open on their nature and interaction types. This motivates experimental efforts to investigate the direct detection of these particles with various techniques. In particular, experiments offering a model independent signature for the presence of Dark Matter (DM) particles in the Galactic halo are mandatory. In this paper some general arguments will be summarized and particular care will be given to the results obtained by the DAMA/LIBRA experiment (sensitive mass: ∼250 kg) at the Gran Sasso National Laboratory of the I.N.F.N. by exploiting the model independent DM annual modulation signature with higly radiopure NaI(Tl) target-detectors. Cumulatively with the former DAMA/NaI (sensitive mass: ∼100 kg) an exposure of 1.17 ton yr, collected over 13 annual cycles, has been released so far; a model independent evidence of the presence of DM particles in the galactic halo is supported at 8.9 ρ confidence level (C.L.). In addition, experimental and theoretical uncertainties and their implications in the interpretation and comparison of different kinds of results will be shortly addressed. Some perspectives will be mentioned.

DARK MATTER INVESTIGATION BY DAMA AT GRAN SASSO

Experimental observations and theoretical arguments at Galaxy and larger scales have suggested that a large fraction of the Universe is composed by Dark Matter particles. This has motivated the DAMA experimental efforts to investigate the presence of such particles in the galactic halo by exploiting a model independent signature and very highly radiopure setup in deep underground. Few introductory arguments are summarized before presenting a review of the present model independent positive results obtained by the DAMA/NaI and DAMA/LIBRA setups at the Gran Sasso National Laboratory of the INFN. Implications and model dependent comparisons with other different kinds of results will be shortly addressed. Some arguments put forward in literature will be confuted.

Dark matter particles in the galactic halo: DAMA/LIBRA results and perspectives

AbstractMost of the Universe is Dark and a large fraction of it should be made of relic particles; many possibilities are open on their nature and interaction types. Thus, their investigation is an outstanding issue in the field; for this purpose experiments offering a model independent signature for the presence of Dark Matter (DM) particles in the Galactic halo are mandatory. In this paper the DAMA/LIBRA results are described. In particular, the DAMA/LIBRA experiment is mainly devoted to the investigation of DM particles in the Galactic halo by exploiting the model independent DM annual modulation signature. The present DAMA/LIBRA and the former DAMA/NaI (exposed masses: ≈︁ 250 kg and ≈︁ 100 kg of highly radiopure NaI(Tl), respectively) experiments have released so far a total exposure of 1.17 ton × yr collected over 13 annual cycles; they provide a model independent evidence of the presence of DM particles in the galactic halo at 8.9 σ C.L.. Future perspectives are mentioned.

Model Independent Signatures of New Physics in the Inflationary Power Spectrum

We compute the universal generic corrections to the inflationary power spectrum due to unknown high-energy physics. We arrive at this result via a careful integrating out of massive fields in the "in-in" formalism yielding a consistent and predictive low-energy effective description in time-dependent backgrounds. We find that the power spectrum is universally modified at order H/M, where H is the scale of inflation. This is qualitatively different from the universal corrections in time-independent backgrounds, and it suggests that such effects may be present in upcoming cosmological observations.

Seeing through the string landscape—a string hunter's companion in particle physics and cosmology

In this article we will overview several aspects of the string landscape, namely intersecting D-brane models and their statistics, possible model independent LHC signatures of intersecting brane models, flux compactification, moduli stabilization in type II compactifications, domain wall solutions and brane inflation.

Direct searches for dark matter particles (above LN2 temperature)

Experimental observations and theoretical considerations have shown that a large part of the Universe is made of Dark Matter particles; this has currently motivated a large experimental effort to investigate them by direct detection approaches. In particular, several techniques are developed. A short review of those that use target at temperature above 77 K is summarized, with particular care to the approaches able to offer a suitable model-independent signature. Some perspectives will also be mentioned.

Supernova neutrino physics with next-generation water-Cherenkov detectors

We investigate the discovery potential of a possible future water-Cherenkov detector (0.4 Mton of fiducial mass) in providing information on supernova neutrino flavor transitions with unprecedented statistics. In this context, we study the effects of the shock-wave propagation on the observable neutrino signal and present an appropriate strategy to monitor model-independent signatures. We also discuss the perspectives for the detection of supernova relic neutrinos, with and without the addition of gadolinium.

Quantum reflection by Casimir–van der Waals potential tails

We study the reflectivity of Casimir--van der Waals potentials, which behave as $\ensuremath{-}{C}_{4}{/r}^{4}$ at large distances and as $\ensuremath{-}{C}_{3}{/r}^{3}$ at small distances. The overall behavior of the reflection amplitude R depends crucially on the parameter $\ensuremath{\rho}=\sqrt{2M}{C}_{3}/(\ensuremath{\Elzxh}\sqrt{{C}_{4}})$ which determines the relative importance of the $\ensuremath{-}{1/r}^{3}$ and the $\ensuremath{-}{1/r}^{4}$ parts of the potential. Near threshold, $E={\ensuremath{\Elzxh}}^{2}{k}^{2}/(2M)\ensuremath{\rightarrow}0,$ the reflectivity is given by $|R|\ensuremath{\sim}\mathrm{exp}(\ensuremath{-}2bk),$ with b depending on $\ensuremath{\rho}$ and the shape of the potential at intermediate distances. In the limit of large energies, $\mathrm{ln}|R|$ is proportional to $\ensuremath{-}{k}^{1/3}$ with a known constant of proportionality depending only on ${C}_{3}.$ For small values of $\ensuremath{\rho},$ the reflectivity behaves as for a homogeneous $\ensuremath{-}{1/r}^{3}$ potential in the whole range of energies and does not depend on ${C}_{4}$ or the shape of the potential beyond the $\ensuremath{-}{1/r}^{3}$ region. For moderate and large values of $\ensuremath{\rho},$ the reflectivity depends on ${C}_{4}$ and on the potential shape. For sufficiently large values of $\ensuremath{\rho},$ which are ubiquitous in realistic systems, there is a range of energies beyond the near-threshold region, where the reflectivity shows the high-energy behavior appropriate for a homogeneous $\ensuremath{-}{1/r}^{4}$ potential, i.e., $\mathrm{ln}|R|$ is proportional to $\ensuremath{-}\sqrt{k}$ with a proportionality constant depending only on ${C}_{4}.$ This conspicuous and model-independent signature of the Casimir effect is illustrated for the reflectivities of neon atoms scattered off a silicon surface, which were recently measured by Shimizu [Phys. Rev. Lett. 86, 987 (2001)].

Scalars from Top-Condensation Models at Hadron Colliders

We study the production and decay of neutral scalars and pseudo-scalars at hadron colliders, in theories where the top-quark mass is the result of a $t\bar t$ condensate. We show that the dominant decay channel for masses below the $t\bar t$ threshold is the flavor changing mode $tc$. This is a consequence of the non-universal nature of the underlying interactions in all top-condensation models and provides a model-independent signature of these scenarios. We show that an upgraded Tevatron is sensitive to a sizeable region of the interesting parameter space and that the LHC will highly constrain these models through this flavor violating channel.