arXiv subjects

R. Foot

Publications and source records attributed to R. Foot.

At least 37 records · Page 2Linked to original sources

arXiv2013

Direct detection experiments explained with mirror dark matter

Recently, the CDMS/Si experiment has observed a low energy excess of events in their dark matter search. In light of this new result we update the mirror dark matter explanation of the direction detection experiments. We find that the DAMA, CoGeNT, CRESST-II and CDMS/Si data can be simultaneously explained by halo $\sim Fe'$ interactions provided that $v_{rot} \approx 200$ km/s. Other parameter space is also possible. Forthcoming experiments, including CDMSlite, CDEX, COUPP, LUX, C-4,... should be able to further scrutinize mirror dark matter and closely related hidden sector models in the near future.

astro-ph.CO↗

arXiv2013

Thin disk of co-rotating dwarfs: a fingerprint of dissipative (mirror) dark matter?

Recent observations indicate that about half of the dwarf satellite galaxies around M31 orbit in a thin plane approximately aligned with the Milky Way. It has been argued that this observation along with several other features can be explained if these dwarf satellite galaxies originated as tidal dwarf galaxies formed during an ancient merger event. However if dark matter is collisionless then tidal dwarf galaxies should be free of dark matter - a condition that is difficult to reconcile with observations indicating that dwarf satellite galaxies are dark matter dominated. We argue that dissipative dark matter candidates, such as mirror dark matter, offer a simple solution to this puzzle.

astro-ph.GA↗

arXiv2013

Galactic structure explained with dissipative mirror dark matter

Dissipative dark matter, such as mirror dark matter and related hidden sector dark matter candidates, requires an energy source to stabilize dark matter halos in spiral galaxies. It has been proposed previously that supernovae could be the source of this energy. Recently, it has been argued that this mechanism might explain two galactic scaling relations inferred from observations of spiral galaxies. One of which is that $ρ_0 r_0$ is roughly constant, and another relates the galactic luminosity to $r_0$. [$ρ_0$ is the dark matter central density and $r_0$ is the core radius.] Here we derive equations for the heating of the halo via supernova energy, and the cooling of the halo via thermal bremsstrahlung. These equations are numerically solved to obtain constraints on the $ρ_0, \ r_0$ parameters appropriate for spiral galaxies. These constraints are in remarkable agreement with the aforementioned scaling relations.

astro-ph.CO↗

arXiv2013

Hidden sector dark matter explains the DAMA, CoGeNT, CRESST-II and CDMS/Si experiments

We examine data from the DAMA, CoGeNT, CRESST-II and CDMS/Si direct detection experiments in the context of multi-component hidden sector dark matter. The models considered feature a hidden sector with two or more stable particles charged under an unbroken $U(1)'$ gauge interaction. The new gauge field can interact with the standard $U(1)_Y$ via renormalizable kinetic mixing, leading to Rutherford-type elastic scattering of the dark matter particles off ordinary nuclei. We consider the simplest generic model of this type, with a hidden sector composed of two stable particles, $F_1$ and $F_2$. We find that this simple model can simultaneously explain the DAMA, CoGeNT, CRESST-II and CDMS/Si data. This explanation has some tension with the most recent results from the XENON100 experiment.

hep-ph↗

arXiv2013

Mirror dark matter interpretations of the DAMA, CoGeNT and CRESST-II data

The CRESST-II collaboration have announced evidence for the direct detection of dark matter in 730 kg-days exposure of a CaWO$_4$ target. We examine these new results, along with DAMA and CoGeNT data, in the context of the mirror dark matter framework. We show that all three experiments can be simultaneously explained via kinetic mixing induced elastic scattering of a mirror metal component off target nuclei. This metal component can be as heavy as Fe$'$ if the galactic rotational velocity is relatively low: $v_{rot} \stackrel{<}{\sim} 220$ km/s. This explanation is consistent with the constraints from the other experiments, such as CDMS/Ge, CDMS/Si and XENON100 when modest $\sim 20-30%$ uncertainties in energy scale are considered.

hep-ph↗

arXiv2013

Top quark forward-backward asymmetry from SU(N_c) color

We argue that the $t \bar t$ production asymmetry observed at the tevatron might be simply explained if the standard $SU(3)_c$ QCD theory is extended to $SU(N_c)$ which is spontaneously broken at a scale just above the weak scale. The extended gauge interactions amplify the radiative QCD contribution to the asymmetry and can potentially explain the observations if $N_c \stackrel{>}{\sim} 5$. This explanation requires a relatively low $SU(N_c)$ symmetry breaking scale $\stackrel{<}{\sim} 0.5-1$ TeV. We check that such a low $SU(N_c)$ symmetry breaking scale is consistent with current collider data. Importantly this scenario predicts an abundance of striking phenomena which will be probed at the LHC. The $SU(N_c)$ model also illustrates the idea that a beyond standard model contribution to the $t \bar t$ asymmetry might arise primarily via radiative corrections rather than at tree-level.

hep-ph↗

arXiv2013

Implications of mirror dark matter kinetic mixing for CMB anisotropies

Mirror dark matter is a dissipative and self-interacting multiparticle dark matter candidate which can explain the DAMA, CoGeNT and CRESST-II direct detection experiments. This explanation requires photon-mirror photon kinetic mixing of strength $ε\sim 10^{-9}$. Mirror dark matter with such kinetic mixing can potentially leave distinctive signatures on the CMB anisotropy spectrum. We show that the most important effect of kinetic mixing on the CMB anisotropies is the suppression of the height of the third and higher odd peaks. If $ε\stackrel{>}{\sim} 10^{-9}$ then this feature can be observed by the PLANCK mission in the near future.

astro-ph.CO↗

arXiv2012

Differentiating hidden sector dark matter from light WIMPs with Germanium detectors

Light WIMP dark matter and hidden sector dark matter have been proposed to explain the DAMA, CoGeNT and CRESST-II data. Both of these approaches feature spin independent elastic scattering of dark matter particles on nuclei. Light WIMP dark matter invokes a single particle species which interacts with ordinary matter via contact interactions. By contrast hidden sector dark matter is typically multi-component and is assumed to interact via the exchange of a massless mediator. Such hidden sector dark matter thereby predicts a sharply rising nuclear recoil spectrum, $dR/dE_R \sim 1/E_R^2$ due to this dynamics, while WIMP dark matter predicts a spectrum which depends sensitively on the WIMP mass, $m_χ$. We compare and contrast these two very different possible origins of the CoGeNT low energy excess. In the relevant energy range, the recoil spectra predicted by these two theories approximately agree provided $m_χ\simeq 8.5$ GeV - close to the value favoured from fits to the CoGeNT and CDMS low energy data. Forthcoming experiments including C-4, CDEX, and the MAJORANA demonstrator, are expected to provide reasonably precise measurements of the low energy Germanium recoil spectrum, including the annual modulation amplitude, which should differentiate between these two theoretical possibilities.

hep-ph↗

arXiv2012

Mirror dark matter explanation of the DAMA, CoGeNT and CRESST-II data

Dark matter might reside in a hidden sector which contains an unbroken $U(1)'$ gauge interaction kinetically mixed with standard $U(1)_Y$. Mirror dark matter provides a well motivated example of such a theory. We show that the DAMA, CoGeNT and CRESST-II experiments can be simultaneously explained within this hidden sector framework. An experiment in the Southern Hemisphere is needed to test this explanation via a diurnal modulation signal.

astro-ph.CO↗

arXiv2012

Mirror dark matter cosmology - predictions for $N_{eff} [CMB]$ and $N_{eff} [BBN]$

Mirror dark matter interacting with ordinary matter via photon-mirror photon kinetic mixing can explain the DAMA, CoGeNT and CRESSTII direct detection experiments. This explanation requires kinetic mixing of strength $ε\sim 10^{-9}$. Such kinetic mixing will have important implications for early Universe cosmology. We calculate the additional relativistic energy density at recombination, $δN_{eff} [CMB]$. We also calculate the effects for big bang nucleosynthesis, $δN_{eff} [BBN]$. Current hints that both $δN_{eff} [CMB]$ and $δN_{eff} [BBN]$ are non-zero and positive can be accommodated within this framework if $ε\approx few \times 10^{-9}$. In the near future, measurements from the Planck mission will either confirm these hints or constrain $ε\stackrel{<}{\sim} 10^{-9}$.

astro-ph.CO↗

arXiv2012

Diurnal modulation due to self-interacting mirror and hidden sector dark matter

Mirror and more generic hidden sector dark matter models can simultaneously explain the DAMA, CoGeNT and CRESST dark matter signals consistently with the null results of the other experiments. This type of dark matter can be captured by the Earth and shield detectors because it is self-interacting. This effect will lead to a diurnal modulation in dark matter detectors. We estimate the size of this effect for dark matter detectors in various locations. For a detector located in the northern hemisphere, this effect is expected to peak in April and can be detected for optimistic parameter choices. The diurnal variation is expected to be much larger for detectors located in the southern hemisphere. In particular, if the CoGeNT detector were moved to e.g. Sierra Grande, Argentina then a $5 σ$ dark matter discovery would be possible in around 30 days of operation.

hep-ph↗

arXiv2011

Mirror and hidden sector dark matter in the light of new CoGeNT data

The CoGeNT collaboration has recently made available new data collected over a period of 15 months. In addition to more accurately measuring the spectrum of nuclear recoil candidate events they have announced evidence for an annual modulation signal. We examine the implications of these new results within the context of mirror/hidden sector dark matter models. We find that the new CoGeNT data can be explained within this framework with parameter space consistent with the DAMA annual modulation signal, and the null results of the other experiments. We also point out that the CoGeNT spectrum at low energies is observed to obey $dR/dE_R \propto 1/E_R^2$ which suggests that dark matter interacts via Rutherford scattering rather than the more commonly assumed contact (four-fermion) interaction.

hep-ph↗

arXiv2010

Do magnetic fields prevent mirror particles from entering the galactic disk?

Recently it has been suggested that magnetic fields prevent mirror particles from entering the galactic disk, thereby disfavoring the mirror dark matter explanation of the dark matter direct detection experiments. We show that mirror particle self interactions will typically randomize the directions of mirror particles on length scales much shorter than their gyroradius. This means that mirror particles are free to enter the galactic disk and consequently mirror dark matter remains consistent with all experiments and observations.

hep-ph↗

arXiv2010

A comprehensive analysis of the dark matter direct detection experiments in the mirror dark matter framework

Mirror dark matter offers a framework to explain the existing dark matter direct detection experiments. Here we confront this theory with the most recent experimental data, paying attention to the various known systematic uncertainties, in quenching factor, detector resolution, galactic rotational velocity and velocity dispersion. We perform a detailed analysis of the DAMA and CoGeNT experiments assuming a negligible channeling fraction and find that the data can be fully explained within the mirror dark matter framework. We also show that the mirror dark matter candidate can explain recent data from the CDMS/Ge, EdelweissII and CRESSTII experiments and we point out ways in which the theory can be further tested in the near future.

hep-ph↗

arXiv2010

A CoGeNT confirmation of the DAMA signal

The CoGeNT collaboration has recently reported a rising low energy spectrum in their ultra low noise germanium detector. This is particularly interesting as the energy range probed by CoGeNT overlaps with the energy region in which DAMA has observed their annual modulation signal. We show that the mirror dark matter candidate can simultaneously explain both the DAMA annual modulation signal and the rising low energy spectrum observed by CoGeNT. This constitutes a model dependent confirmation of the DAMA signal and adds weight to the mirror dark matter paradigm.

hep-ph↗

arXiv2010

Primordial He' abundance implied by the mirror dark matter interpretation of the DAMA/Libra signal

We compute the primordial mirror helium He' mass fraction emerging from Big Bang nucleosynthesis in the mirror sector of particles in the presence of kinetic mixing between photons and mirror photons. We explore the kinetic mixing parameter (epsilon) values relevant for cosmology and which are also currently probed by the dark matter direct detection experiments. In particular, we find that for epsilon \sim 10^{-9}, as suggested by the DAMA/Libra and other experiments, a large He' mass fraction (Y_{He'} \approx 90%) is produced. Such a large value of the primordial He' mass fraction will have important implications for the mirror dark matter interpretation of the direct detection experiments, as well as for the study of mirror star formation and evolution.

astro-ph.CO↗

arXiv2009

Relevance of the CDMSII events for mirror dark matter

Mirror dark matter offers a framework to explain the existing dark matter direct detection experiments, including the impressive DAMA annual modulation signal. Here we examine the implications of mirror dark matter for experiments like CDMSII/Ge and XENON10 which feature higher recoil energy threshold than the DAMA NaI experiments. We show that the two events seen in the CDMSII/Ge experiment are consistent with the interactions of the anticipated heavy $\sim Fe'$ component. This interpretation of the CDMSII/Ge events is a natural one given that a) mirror dark matter predicts an event rate which is sharply falling with respect to recoil energy and b) that the two observed events are in the low energy region near threshold. Importantly this interpretation of the CDMSII events can be checked by on-going and future experiments, and we hereby predict that the bulk of the events will be in the $E_R \stackrel{<}{\sim} 18$ keV region.

hep-ph↗

arXiv2009

Evidence for mirror dark matter from the CDMS low energy electron recoil spectrum

We point out that mirror dark matter predicts low energy ($E_R \stackrel{<}{\sim} 2$ keV) electron recoils from mirror electron scattering as well as nuclear recoils from mirror ion scattering. The former effect is examined and applied to the recently released low energy electron recoil data from the CDMS collaboration. We speculate that the sharp rise in electron recoils seen in CDMS below 2 keV might be due to mirror electron scattering and show that the parameters suggested by the data are roughly consistent with the mirror dark matter explanation of the annual modulation signal observed in the DAMA/Libra and DAMA/NaI experiments. Thus, the CDMS data offer tentative evidence supporting the mirror dark matter explanation of the DAMA experiments, which can be more rigorously checked by future low energy electron recoil measurements.

hep-ph↗