Abstract. Although the velocity distribution of dark matter is assumed to be generally isotropic, some studies have found that ∼ 25% of the distribution can have anisotropic components. As the directional detection of dark matter is sensitive to both the recoil energy and direction of nuclear recoil, directional information can prove useful in mea- suring the distribution of dark matter. Using a Monte Carlo simulation based on the mod- eled directional detection of dark matter, we analyze the diﬀerences between isotropic and anisotropic distributions and show that the isotropic case can be rejected at a 90% confidence level if O(10 4 ) events can be obtained.
The analysis of signals in directional dark matter (DM) detectors typically assumes that the directions of nuclear recoils can be measured in the Galactic rest frame. However, this is not possible with all directional detection technologies. In nuclear emulsions, for example, the recoil events must be detected and measured after the exposure time of the experiment. Unless the entire detector is mounted and rotated with the sidereal day, the recoils cannot be reoriented in the Galactic rest frame. We examine the effect of this ‘time integration’ on the primary goals of directional detection, namely: (1) confirming that the recoils are anisotropic; (2) measuring the median recoil direction to confirm their Galactic origin; and (3) probing below the neutrino floor. We show that after time integration the DM recoil distribution retains a preferred direction and is distinct from that of Solar neutrino-induced recoils. Many of the advantages of directional detection are therefore preserved and it is not crucial to mount and rotate the detector. Rejecting isotropic backgrounds requires a factor of 2 more signal events compared with an experiment with event time information, whereas a factor of 1.5 − 3 more events are needed to measure a median direction in agreement with the expectation for DM. We also find that there is still effectively no neutrino floor in a time-integrated directional experiment. However to reach a cross section an order of magnitude below the floor, a factor of ∼ 8 larger exposure is required than with a conventional directional experiment. We also examine how the sensitivity is affected for detectors with only 2D recoil track readout, and/or no head-tail measurement. As for non-time-integrated experiments, 2D readout is not a major disadvantage, though a lack of head-tail sensitivity is.
15 Read more
There is strong evidence from a variety of sources to suggest that 85% of the matter in the Universe is in the form of dark matter . One possibility favored by theories beyond the Standard Model of particle physics is that dark matter consists of Weakly Interacting Massive Particles (WIMPs) . As such, a large, international effort has been underway for decades to search for the rare, low-energy recoil events produced by WIMP interactions . The DAMA collaboration measures an annual modulation in their event rate that they interpret as a WIMP detection . However, other experimental results are in tension with this claim [4-8]. The primary goal of direct ional dark matter detectors is to provide a „smoking gun‟ signature of dark matter [9, 10]. Such experiments seek to measure not only the energy, but also the direction of WIMP-induced nuclear recoils, thereby confirming their signals as galactic in origin. Numerous studies have shown the power of a directional signal, e.g. [11, 12]. Instead of order 10 4 events required for confirmation via the annual modulation signature, only of order 10-100 events are required with a directional signature , assuming zero background. Additionally, instead of the easily mimicked annual modulation, the directional signal is fixed to the galactic coordinate system and is therefore less prone to false-positive detections. In recent years, several ideas for directional detection technologies have been proposed and revived [14-19]. At present, however, the only demonstrated, directional, detection technology to be deployed is recoil tracking in low- pressure gas time projection chambers (TPCs) .
27 Read more
Abstract. Direct dark matter searches are promising techniques to identify the nature of dark matter particles. The directional information is a distinctive directional property of the dark matter distribution against the cosmic background. The NEWSdm project is a unique experiment among several directional detection projects because of its solid-state detector. The expected signal of WIMP-induced nuclear recoil in such a detector is sub- micron scale. The high-resolution nuclear emulsion and the special readout method were developed for such extremely short tracks. Technologies for background identification and large-scale analysis are developing toward several kg scale experiment at Gran Sasso underground laboratory in the coming years
Evidence in support of the dark matter hypothesis may come from indirect measurements, such as measurement of neutrinos from dark matter annihilations in the Sun, or from accelerator searches, such as through searches for supersymmetric particles at the LHC. However, a truly robust signature is given by direct detection of WIMPS interacting with ordinary matter. Due to the smallness of the WIMP cross sections and the difficulty of reducing and predicting backgrounds, measurement of the recoil direction of elastically scattered nuclei is widely regarded as being the most robust direct detection signal . At present low pressure TPCs, such as DRIFT, offer the best technology for providing such measurements [1, 3].
24 Read more
The thin film cathode of (5) was developed to tackle the recoil-like backgrounds discussed in section 2, and is described in detail in Loomba et al. (2012) . Briefly, making the cathode thin and thus more transparent to alpha particles increases the probability of background recoils being vetoed by detection of the associated alpha particle. Monte Carlo simulations predict that moving from a 20 µm diameter steel wire cathode to a 0 . 9 µm thin film alumnised Mylar cathode reduces the fraction of lost alpha particles from the decay of 218 Po ( 214 Po) from 36% (25%) to 1.2% (0.8%). The difference is a consequence of the differing energies of the two alpha particles: 6 MeV and 7.69 MeV, respectively.
16 Read more
A potentially clear and robust signature would be the detection of the direction of WIMP induced nuclear recoil signals [21, 24]. Such a directional measurement can allow for discrimination of terrestrial, isotropic or solar neutrino backgrounds from WIMP-induced recoils peaked away from Cygnus [22, 25, 26]. The DRIFT , NEWAGE , MIMAC , DMTPC  and D 3  collaborations have developed directional WIMP search time projection chambers. The NEWSdm experiment  has also made progress using nuclear emulsions to measure directions of nuclear recoil tracks. Other methods, for instance columnar recombination in Xenon targets , use of polarised 3 He , carbon nanotube  and anisotropic crystal scintillator  targets are being considered. However, there is concern that multiple scattering of nuclear recoil ionization signals in liquid and solid state target detectors can obscure the directional information of tracks . Also, ranges of nuclear recoils are larger in low-pressure gas TPCs, allowing for better track reconstruction, including both the 3D range component R 3 , and the vector direction (sense) of the recoil.
18 Read more
Detection and characterisation of dark matter (DM) - thought to be Weakly In- teracting Massive Particles (WIMPs) [1, 2, 3] in a direction sensitive nuclear recoil detector with a suitable target material, is a major goal of the DM search commu- nity [4, 5, 6, 7]. This technology offers the potential to discriminate WIMP candidate events with galactic signature from terrestrial backgrounds/artefacts and hence, can probe below the so-called neutrino floor [8, 9, 10]. The use of low pressure gas Time Projection Chamber (TPC) technology, in which ionisation electrons from the nuclear recoil tracks are drifted to a charge readout plane and recorded for reconstruction, of- fers a route to achieving this goal. This is with potentials for low energy threshold and low background operations, including active electron recoil discrimination in the low WIMP mass parameter space.
18 Read more
The design of DRIFT-II, with thin-film central cathode and two back-to-back MWPC detectors (see section 1), allows identification of several classes of radon-related alpha background as detailed in Burgos et al. (2008) . Notable here are so-called ‘gold-plated cathode-crossers’ (GPCCs) that, though not a background for dark matter searches, can provide an unambiguous tracer of radon in the experiment. The main characteristic of GPCCs is that charge is detected in time coincidence on both sides of the detector, and that both tracks start and end within the fiducial volume. GPCCs are thus ‘fully contained’ events that originated in the bulk of the gas and crossed the central cathode plane. The low (∼ 1 Hz) raw event rate and analysis cuts make time-coincident events from separate sources extremely unlikely (< 1 coincidence every five years).
20 Read more
The search for weakly interacting massive particles (WIMPs) by direct detection faces an en- croaching background due to coherent neutrino-nucleus scattering. As the sensitivity of these ex- periments improves, the question of how to best distinguish a dark matter signal from neutrinos will become increasingly important. A proposed method of overcoming this so-called “neutrino floor” is to utilize the directional signature that both neutrino and dark matter induced recoils possess. We show that directional experiments can indeed probe WIMP-nucleon cross-sections below the neutrino floor with little loss in sensitivity due to the neutrino background. In particular we find at low WIMP masses (around 6 GeV) the discovery limits for directional detectors penetrate be- low the non-directional limit by several orders of magnitude. For high WIMP masses (around 100 GeV), the non-directional limit is overcome by a factor of a few. Furthermore we show that even for directional detectors which can only measure 1- or 2-dimensional projections of the 3-dimensional recoil track, the discovery potential is only reduced by a factor of 3 at most. We also demonstrate that while the experimental limitations of directional detectors, such as sense recognition and finite angular resolution, have a detrimental effect on the discovery limits, it is still possible to overcome the ultimate neutrino background faced by non-directional detectors.
16 Read more
Background rejection in DRIFT-II has now reached a point where the experiment is becoming statistics limited, highlighting the need for a scale-up. DRIFT-III is a proposed new modular directional dark matter detector, incorporating all the technological advances that have been made on previous iterations of DRIFT, and will move directional dark matter detection toward the ton scale. A cartoon of a proposed DRIFT-III Module (DTM) is shown in figure 5. Each module consists of an instrumented 70 kV thin-film cathode and a transparent MWPC plane capable of detecting events on either side, separated by field cage modules either side of the cathode. In this way, a large fiducial volume can be created simply by slotting in additional DTMs. The MWPC planes will use new ‘resistive wire’ technology, prototypes of which are currently being developed for use in DRIFT-II. Instead of measuring ∆x and ∆y using orthogonal anode and field wire planes, the new detectors consist of 1mm pitch alternating anode and field wires oriented in a single direction, with a recoil’s extent in the direction parallel to the wires being recovered by charge-dividing readout at either end of the anode wires.
Abstract. The nature of Dark Matter is one of the fundamental questions to be answered. Direct Dark Matter searches are focussed on the development, construction, and operation of detectors looking for the scattering of Weakly Interactive Massive Particles (WIMPs) with target nuclei. The measurement of the direction of WIMP-induced nuclear recoils is a challenging strategy to extend dark matter searches beyond the neutrino floor and pro- vide an unambiguous signature of the detection of Galactic dark matter. Current direc- tional experiments are based on the use of gas TPC whose sensitivity is strongly limited by the small achievable detector mass. NEWSdm is an innovative directional experiment proposal based on the use of a solid target made by newly developed nuclear emulsion films and read-out systems achieving a position accuracy of 10 nm.
are analyzed in the Big-Bang model, existence of a new kind of energy that fills the space is required which is termed as Dark Energy. It has a negative pressure and negative gravitational effect causing a gravitational repulsion. As the Universe expands, Dark Energy stays at nearly constant energy density and, as the matter in the Universe thins out, the Dark Energy begins to dominate. The repulsive effect of Dark Energy seems to guarantee that the Universe might continue to expand forever. It is now a great challenge to theoretical physicists to give a consistent model for the Dark Energy in addition to Dark Matter. In the Einstein field equation this may be achieved by a modification of the gravitational sector  or the matter sector . The work in this direction is now in progress worldwide to unravel the mystery of the Universe. Emergent Universe model in a flat Universe is another interesting model of the Universe which can be obtained with a non-linear equation of state . In the emergent Universe scenario the initial size of the Universe was large enough so that quantum gravity effect is not important. The horizon and flatness problems do not arise. In the EU scenario, the Universe evolves from a static phase in the infinite past into an inflationary phase at a later epoch. In the usual description with a scalar field it is shown that a Universe starts expanding from the above phase, later on smoothly joins with a stage of exponential expansion followed by standard reheating and then approaches the classical thermal radiation dominated era of the conventional Big-Bang cosmology. The matter in the Universe may be considered as a composition of three kinds of fluids depending on EoS parameter. In the model one of the compositions of matter is Dark Energy. It permits an accelerating Universe which is supported by observations.
The most popular candidates on Dark Matter (DM) carrier are weakly interacting massive particles (WIMP). However, such particles are discovered not yet and there are only rigid restrictions on the cross-sections of WIMP-nucleon interactions . So, alternative scenarios are disscussed in literature, for instance, the scenario with strongly interacting massive par- ticles (SIMP) -. In this report, we consider the scenario with hadronic DM particles, which is special case of SIMP one. The DM particle M, in this case, consists of new heavy quark Q and standard light quark q, that is M = (qQ), where Q possess standard strong in- teractions. The most developed variants of new heavy quark origin are the following: 4-th generation of heavy fermions -, mirror or chiral-symmetric models [11, 12] and the extensions of Standard Model (SM) with singlet quark -. Here, we consider the sec- ond and third variant of hadronic DM. It was shown in the works [19, 20], that the scenario of hadronic DM does not contradict to the electro-weak restrictions on new physics and the experimental data on abundence of anomalous elements now. Strong QCD-type interaction of new quark Q with ordinary one leads to the forming of coupled states - two-quark (meson) and three-quark (baryon) heavy hadrons. Here, we consider the simplest two-quark states M = (qQ) and show that the lightest neutral new meson can be suggested as candidate on DM particles.
A main problem in astrophysics is the discovery, about two decades ago, that our Universe expansion is acceler- ating, instead of slowing down as predicted by the Big Bang theory  Scientists hypothesize the existence of an anti-gravity energy field dubbed Dark Energy (DE). It has been claimed that the identification and understand- ing of that DE would be the greatest accomplishment of the century .
10 Read more
From this it follows that space is uniform and isotropic. If we mentally separate some regions of size 300 Mpc in a certain volume of the Universe and count the number of galaxies in each of them, it will be almost the same for all the regions. The same result will be obtained in case of clusters and super clusters. A volume with its cross size of 300 Mpc, starting from which the space distribu- tion of galaxies is approximately uniform, is called a uniformity cell in the Universe. In the nearest region, however, in the volume observed by Hubble the distribu- tion of matter is not uniform at all. On the contrary, the galaxies are distributed here unevenly forming with their size of about 1 Mpc.
11 Read more
Solution of this problem, as it turns out, has to do extremely unusually and affecting the fundamental philosophical questions of astrophysical objects—the dark matter discovered in 1932-33 by Jan Hendrik Oort and Fritz Zwikky and dark energy discovered in 1998-99 by the Nobel Prize winners Saul Perlmutter, Brian P. Schmidt and Adam G. Riess  . They were called dark because they turned out to be totally incomprehensible and absolutely invisible. Therefore they were able to detect them only indirectly by the effect of gravitational lens- ing. Moreover, they do not contain any of the chemical elements known to us and any known subatomic particles. It would seem, therefore, that the existence of this phenomenon destroys the modern understanding of the term “substance” and rejects physics in its development to the thousands of years ago.
17 Read more
As predicted by space dynamics, the gravitational potential determined within the galactic disk, with base in Equation (18) (please see Figure 6), is considerably more leveled than the potentials computed with base in the current gravitational theories. The velocity gradient in the galactic velocity field and hence the gravitational ac- celeration of a body resting within the galactic disk, predicted by space dynamics, is very low and notwith- standing the stars move along circular orbits round the galactic center (no need of a central force field). They are carried around the galactic nucleus by the moving QS; likewise the planets are carried round the sun by the solar Keplerian velocity field of the QS and need no centripetal force to move so. The impasse of the current theories with these observations arises because, in order to account for the circular motion of the stars round the galactic center they absolutely need a gradient of the gravitational potential (centripetal force), pointing to the gravita- tional center. The absence of such a gradient gives rise to an unsolvable paradox. Instead of amending the theo- ries, people preferred to believe in the presence of invisible halo of dark matter crating such a gradient.
15 Read more
In this regard, then, it would perhaps be interesting to give a detailed look at the detection issues arising in cases when one moves just one step beyond the SMS approach, i.e., when one tries to build models that are halfway in between those SMS characterized by just one type of mediator and interaction mechanism, and a UV complete model. We take this approach in this paper, in which we combine existing SMS in pairs, with the goal to somewhat mimic the behavior of a developed UV theory without at the same time drastically increasing the number of parameters, or including the full spectrum of a specific model. We only consider SMS and parameter ranges for which the spin-independent scattering cross section is substantial, so that a comparison between the limits from DD and the LHC is always possible. The combinations involve three popular SMS characterized by vector mediators, scalar mediators, and colored scalar mediators, and we take the DM particle to be a Dirac fermion. The models given here represent only a few motivated examples of the many combinations that can be constructed. We dedicate special attention to the blind spots for DD, which stem from interference effects among different diagrams. We show that each of the emerging blind spots can be tested in Run 2 of the LHC, by different experimental strategies. Our study is thus complementary to previous studies in this direction [49–55], although, to the best of our knowledge, the combinations we consider here have not been analyzed before in this setting.
28 Read more
background. It follows from experimental practice that suppressing these background electrons is a most challenging and important task because they persist despite the use of highly sophisticated background suppression system (underground laboratories from cosmic rays, passive and active protection, super high pure materials). In fact, sensitivity limits of experimental designed to directly detect WIMPs depends on solving these problems. One approach to suppressing this background component is to detect two signals simultaneously (e.g. phonon + ionization or ionization + scintillation) in ‘hybrid’ detection (see Fig.1). A neutron background can be suppressed by using the multiple scattering signature absent in the case of WIMPs. Generally speaking, the difficulty of direct experiments in the search for WIMPs is determined by the following factors: (a) a very small WIMP-nucleon scattering cross section ( < 10 − 6 pb ) necessitating a large sensitive detector mass; (b) the low efficiency of measurement of small energies of recoil nuclei ( ~ 10 100 − keV ) necessitating the use of detectors with the threshold of several keV ; (c) a very high CR and natural radioactivity background necessitating location of the detectors in underground laboratories and the use of protective shields or materials free from radioactive admixtures.