We revisit the detection of luminous dark matter in direct detection experiments. In this scenario, dark matter scatters endothermically to produce an excited state, which decays to produce a photon. We explore ways in which the electron recoil signal from the decay photon can be differentiated from other potential electron recoil signals with a narrow spectral shape. We find that larger volume/exposure xenon detectors will be unable to differentiate the signal origin without significant improvements in detector energy resolution of around an order of magnitude. We also explore what can be learned about a generic luminous dark matter signal with a higher resolution detector. Motivated by the advancements in energy resolution by solid-state detectors, we find that sub-eV resolution enables the discovery of LDM in the presence of background levels that would otherwise make observation impossible. We also find that sub-eV resolution can be used to determine the shape of the luminous dark matter decay spectrum and thus constrain the dark matter mass and velocity distribution.
Cosmic-ray boosted inelastic dark matter from neutrino-emitting active galactic nuclei
Virginia Tech（弗吉尼亚理工大学）；Massachusetts Institute of Technology（麻省理工学院）；Harvard University（哈佛大学）；The Pennsylvania State University（宾夕法尼亚州立大学）；Fermi National Accelerator Laboratory（费米国家加速实验室）；University of Chicago（芝加哥大学）
Direct detection experiments relying on nuclear recoil signatures lose sensitivity to sub-GeV dark matter for typical galactic velocities. This sensitivity is recovered if there exists another source of flux with higher momenta. Such an energetic flux of light dark matter could originate from the decay of mesons produced in inelastic cosmic ray collisions. We compute this novel production mechanism---a cosmic beam dump experiment---and estimate the resulting limits from XENON1T and LZ. We find that the dark matter flux from inelastic cosmic rays colliding with atmospheric nuclei can dominate o…
In this paper, we introduce model-independent data analysis procedures for identifying inelastic WIMP-nucleus scattering as well as for reconstructing the mass and the mass splitting of inelastic WIMPs simultaneously and separately. Our simulations show that, with O(50) observed WIMP signals from one experiment, one could already distinguish the inelastic WIMP scattering scenarios from the elastic one. By combining two or more data sets with positive signals, the WIMP mass and the mass splitting could even be reconstructed with statistical uncertainties of less than a factor of two.
Light non-relativistic components of the galactic dark matter halo elude direct detection constraints because they lack the kinetic energy to create an observable recoil. However, cosmic-rays can upscatter dark matter to significant energies, giving direct detection experiments access to previously unreachable regions of parameter-space at very low dark matter mass. In this work we extend the cosmic-ray dark matter formalism to models of inelastic dark matter and show that previously inaccessible regions of the mass-splitting parameter space can be probed. Conventional direct detection of non-…
We perform a model-independent study of inelastic dark matter at the LHC, concentrating on the parameter space with the mass splitting between the excited and ground states of dark matter above a few hundred MeV, where the direct detection experiments are unlikely to explore. The generic signatures of inelastic dark matter at the LHC are displaced pions together with a monojet plus missing energy, and can be tested at the 7 TeV LHC.
We show that the current sensitivities of direct detection experiments have already reached the interesting parameter space of freeze-in dark matter models if the dark sector is in the inelastic dark matter framework and the excited dark matter state is cosmologically stable. Using results recently presented by the XENON1T experiment, we present constraints on these models. We also show that these models can explain the reported excess in the electron recoil signals if the mass gap between the ground state and the excited state is at keV scale.
We consider inelastic dark matter scenarios with dark photon mediator and a dark Higgs boson. The dark Higgs boson spontaneously breaks the gauge symmetry associated with the dark photon, and gives the mass to the dark photon and the mass difference to dark particles. Such a dark Higgs boson can decay into the dark particles and hence can be another source of the dark particles at collider experiments. We analyze the sensitivity to decays of the excited state into the dark matter and charged particles at the FASER 2 experiment in fermion and scalar inelastic dark matter scenarios. We consider …
Feebly interacting thermal relics are promising dark matter candidates. Among them, scenarios of inelastic Dark Matter evade direct detection by suppressed elastic scattering off atomic nuclei. We introduce inelastic Dirac Dark Matter, a new model with two Dirac fermions in the MeV-GeV mass range. At feeble couplings, dark matter can depart from chemical as well as kinetic equilibrium with the Standard Model before freeze-out. In this case, the freeze-out is driven by conversion processes like coscattering, rather than coannihilation. We show that inelastic Dirac relics are consistent with cos…
We perform an extensive study of the DAMA annual modulation data in the context of inelastic dark matter. We find that inelastic dark matter with mass m > 15 GeV is excluded at the 95% confidence level by the combination of DAMA spectral information and results from other direct detection experiments. However, at smaller m, inelastic dark matter constitutes a possible solution to the DAMA puzzle.
Recent experimental results indicate that the dark matter sector may have a non-minimal structure with a spectrum of states and interactions. Inelastic scattering has received particular attention in light of DAMA's annual modulation signal. Composite inelastic dark matter (CiDM) provides a dynamical origin for the mass splittings in inelastic dark matter models. We show that higher dimensional operators in the CiDM Lagrangian lead to an admixture of inelastic and elastic scattering in the presence of parity violation. This scenario is consistent with direct detection experiments, even when pa…
We present a model independent analysis of inelastic dark matter transitions at direct detection experiments by modifying the elastic methodology of Fitzpatrick, et al. By analyzing the kinematics of inelastic transitions, we find the relevant variables to describe these scattering processes, the primary change being a modification of the $\vec{v}^\perp$ variable. Taking this into account, we list the relevant scattering matrix elements and modify the Mathematica package of Anand, et al. to calculate the necessary form factors. As an application, we determine the matrix elements of inelastic s…
We consider a dark sector containing a pair of almost degenerate states coupled to the Standard Model through a dark photon mediator. This set-up constitutes a simple realization of the inelastic dark matter scenario. The heaviest dark state is long-lived, in the limit of a small kinetic mixing among the dark photon and the Standard Model hypercharge gauge boson, and/or of a small mass splitting among the dark states. We study the prospects for detection of this scenario at proposed LHC experiments dedicated to search for long-lived particles, namely FASER, MATHUSLA, CODEX-b, AL3X, MAPP, ANUBI…
The perturbative QCD predictions concerning deep inelastic scattering at low $x$ are summarized. The theoretical framework based on the leading log $1/x$ resummation and $k_t$ factorization theorem is described. The role of studying final states in deep inelastic scattering for revealing the details of the underlying dynamics at low $x$ is emphasised and some dedicated measurements, like deep inelastic scattering accompanied by an energetic jet, the measurement of the transverse energy flow and deep inelastic diffraction, are briefly discussed.
We explore the reach of low-background experiments made of small quantities of heavy nuclear isotopes in probing the parameter space of inelastic dark matter that is kinematically inaccessible to classic direct detection experiments. Through inelastic scattering with target nuclei, dark matter can yield a signal either via nuclear recoil or nuclear excitation. We present new results based on this approach, using data from low-energy gamma quanta searches in low-background experiments with Hf and Os metal samples, and measurements with CaWO$_4$ and PbWO$_4$ crystals as scintillating bolometers.…
Peaking consistently in June for nearly eleven years, the annual modulation signal reported by DAMA/NaI and DAMA/LIBRA offers strong evidence for the identity of dark matter. DAMA's signal strongly suggest that dark matter inelastically scatters into an excited state split by O(100 keV). We propose that DAMA is observing hyperfine transitions of a composite dark matter particle. As an example, we consider a meson of a QCD-like sector, built out of constituent fermions whose spin-spin interactions break the degeneracy of the ground state. An axially coupled U(1) gauge boson that mixes kinetical…
The $O(α^2\log(Q^2/m_e^2))$ leptonic QED corrections to unpolarized deeply inelastic electron-nucleon scattering are calculated in the mixed variables.
Inelastic dark matter is an interesting scenario for light thermal dark matter which is fully consistent with all cosmological probes as well as direct and indirect dark matter detection. The required mass splitting between dark matter $χ_1$ and its heavier twin $χ_2$ is naturally induced by a dark Higgs field which also provides a simple mechanism to give mass to the dark photon $A'$ present in the setup. The corresponding dark Higgs boson $h'$ is naturally the lightest dark sector state and therefore decays into Standard Model particles via Higgs mixing. In this work we study signatures with…
Neutron stars can provide new insight into dark matter properties, as these dense objects capture dark matter particles very efficiently. It has recently been shown that the energy transfer in the dark matter capture process can lead to appreciable heating of neutron stars, which may be observable with forthcoming infra-red telescopes. We examine this heating in the context of inelastic dark matter, for which signals in conventional nuclear-recoil based direct detection experiments are highly suppressed when the momentum transfer is small compared to the mass splitting between dark matter stat…
We calculate azimuthal asymmetries and the Callan-Gross $R$-ratio for semi-exclusive pion production in deep inelastic scattering taking into account higher twist effects. Our results are qualitatively different from the QCD-improved parton model predictions for semi-inclusive deep inelastic scattering.
Using the "Quality Factor" (QF) method, we analyse the scaling properties of deep-inelastic processes at HERA and fixed target experiments for x<10^{-2}.
Recent measurements of inclusive deep inelastic scattering differential cross-section in the range 1.5 \gev2\le Q^2\le 30000 \gev2 and 5\cdot 10^{-6}\le x\le 0.65 are presented. Phenomenological analyses performed from these measurements are also described.
We consider the capture of inelastic dark matter in white dwarves by inelastic spin-independent scattering on nuclei. We show that if the dark matter annihilates to standard-model particles then, under the assumption of primordial globular cluster formation, the observation of cold white dwarves in the globular cluster M4 appears inconsistent with explanations of the observed DAMA/LIBRA annual modulation signal based on spin-independent inelastic dark matter scattering. Alternatively if the inelastic dark matter scenario were to be confirmed and it was found to annihilate to standard-model par…
I discuss the instanton-induced contributions to the coefficient functions in front of parton densities. They correspond to the spherically symmetric particle production at the level of $10^{-2}-10^{-5}$ of the total cross section of deep inelastic scattering from the parton.
We argue that the difference between the structure functions corresponding to deep inelastic scattering with and without heavy quarks in the current fragmentation region scales at high Q^2 and fixed (low) x.
We investigate the power-suppressed corrections to fragmentation functions in flavour-singlet deep inelastic lepton scattering, to complement the previous results for the non-singlet contribution. Our method is a dispersive approach based on an analysis of Feynman graphs containing massive gluons. As in non-singlet deep inelastic scattering we find that the leading corrections are proportional to 1/Q^2.
Composite dark matter is a natural setting for implementing inelastic dark matter - the O(100 keV) mass splitting arises from spin-spin interactions of constituent fermions. In models where the constituents are charged under an axial U(1) gauge symmetry that also couples to the Standard Model quarks, dark matter scatters inelastically off Standard Model nuclei and can explain the DAMA/LIBRA annual modulation signal. This article describes the early Universe cosmology of a minimal implementation of a composite inelastic dark matter model where the dark matter is a meson composed of a light and …
We study the azimuthal angle decorrelation of forward jets in Deep Inelastic Scattering. We make predictions for this observable at HERA describing the high energy limit of the relevant scattering amplitudes with quasi-multi-Regge kinematics together with a collinearly improved evolution kernel for multiparton emissions.
Charmed meson production in semi-inclusive deep inelastic scattering is investigated in the color dipole formalism. The transverse momentum distributions are calculated. We find good agreement with the H1 data using a hard fragmentation function.
We investigate a simplified version of the ACOT prescription for calculating deeply inelastic scattering from Q^2 values near the squared mass M_H^2 of a heavy quark to Q^2 much larger than M_H^2.
We consider an inelastic dark matter model, where a fermion is charged under a broken U(1) gauge symmetry, and introduce a tiny Majorana mass term to split the fermion into two states with the light one being a dark matter candidate. If the gauge boson is light, it can mediate both elastic and inelastic dark matter self-interactions in dark halos, leading to observational consequences. Using a numerical technique based on partial wave analysis, we accurately calculate the elastic and inelastic self-scattering cross sections. We assume a thermal freeze-out scenario and fix the gauge coupling co…
We calculate the fully differential Next-to-Leading Order (NLO) corrections to (longitudinally) polarized dijet production in deep inelastic scattering, featuring both neutral current and charged current processes. We also analyze their phenomenological impact in the Electron-Ion Collider (EIC) kinematics.
Direct detection experiments aim at the detection of dark matter in the form of weakly interacting massive particles (WIMPs) by searching for signals from elastic dark matter nucleus scattering. Additionally, inelastic scattering in which the nucleus is excited is expected from nuclear physics and provides an additional detectable signal. In the context of a low-energy effective field theory we investigate the experimental reach to these inelastic transitions for xenon-based detectors employing a dual-phase time projection chamber. We find that once a dark matter signal is established, inelast…
We study luminous dark matter signals in models with inelastic scattering. Dark matter $χ_1$ that scatters inelastically off elements in the Earth is kicked into an excited state $χ_2$ that can subsequently decay into a monoenergetic photon inside a detector. The photon signal exhibits large sidereal-daily modulation due to the daily rotation of the Earth and anisotropies in the problem: the dark matter wind comes from the direction of Cygnus due to the Sun's motion relative to the galaxy, and the rock overburden is anisotropic, as is the dark matter scattering angle. This allows outstanding s…
Dark matter in the form of weakly interacting massive particles is predicted to become gravitationally captured and accumulate in stars. While the subsequent annihilations of such particles lead to the injection of energy into stellar cores, elastically scattering dark matter particles do not generally yield enough energy to observably impact stellar phenomenology. Dark matter particles which scatter inelastically with nuclei (such that they reconcile the annual modulation reported by DAMA with the null results of CDMS and other experiments), however, can be captured by and annihilate in compa…
We give an overview of jet physics in deeply inelastic scattering at HERA. The problem of jet definitions, the scale dependence of jet cross sections and some applications are discussed. (Talk presented at the Workshop on Deeply Inelastic Scattering and QCD, Paris, April 1995. To appear in the proceedings.)
The pomeron structure function is extracted from the latest H1 data and are subject to a QCD analysis. The result shows evidence for gluon recombination.
A new package, DISPred, is described. The package can be used to calculate ep deep inelastic scattering cross sections at Born level in Electroweak theory and at both leading and next-to-leading order in QCD.
The non-valence spin-flavor structure of the nucleon extracted from semi-inclusive measurements of polarized deep inelastic scattering depends strongly on the transverse momentum of the detected hadrons which are used to determine the individual polarized sea distributions. This physics may explain the recent HERMES observation of a positively polarized strange sea through semi-inclusive scattering, in contrast to the negative strange sea polarization deduced from inclusive polarized deep inelastic scattering.
We identify and calculate the instanton-induced contributions to deep inelastic scattering which correspond to nonperturbative exponential corrections to the coefficient functions in front of parton distributions of the leading twist.
We explore a novel class of multi-particle dark sectors, called Inelastic Boosted Dark Matter (iBDM). These models are constructed by combining properties of particles that scatter off matter by making transitions to heavier states (Inelastic Dark Matter) with properties of particles that are produced with a large Lorentz boost in annihilation processes in the galactic halo (Boosted Dark Matter). This combination leads to new signals that can be observed at ordinary direct detection experiments, but require unconventional searches for energetic recoil electrons in coincidence with displaced mu…
The brief overview of the definite determinations of the QCD coupling constant $α_s$ from the characteristics of deep-inelastic scattering processes is given.
It is shown that the HERA experimental data on deep inelastic scattering at low values of the scaling variable x < 0.05 are in good agreement with predictions from Generalized Vector Dominance in the full kinematic range from Q2 = 0 (photoproduction) to Q2 = 350 GeV.
I discuss possibilities to observe the instanton-induced contributions to deep inelastic scattering which correspond to nonperturbative exponential corrections to the coefficient functions in front of parton distributions of the leading twist.
We review studies of inelastic meson-meson scattering. In nonperturbative schemes with chiral-perturbation-theory Lagrangians and in models based on effective meson Lagrangians, inelastic meson-meson scattering leads to the successful identification of resonances in meson-meson reactions, adequate inclusion of final state interactions in particle decays, and so on. For mesons of which each consists of a quark and an antiquark, inelastic meson-meson scattering may be caused by quark-antiquark annihilation, quark-antiquark creation, quark interchange, and quark-antiquark annihilation and creatio…
We set tight constraints on the energy loss of hard quarks in nuclear matter from NA3 Drell-Yan measurements. Our estimate then allows for the description of HERMES preliminary deep inelastic scattering data on hadron production.
We investigate the 1/Q^2 power-suppressed corrections to structure functions in the flavour-singlet channel of deep inelastic lepton scattering arising from renormalon insertions into an initial-state gluon, as obtained using the dispersive approach. The pinch technique is used as a convenient tool in the separation of contributions.
General arguments suggest that the non-perturbative background field in QCD may have a non-trivial spin structure. We discuss how this effect may be manifest in semi-inclusive measurements of fast pions in polarised deep inelastic scattering.
