Inelastic frontier: Discovering dark matter at high recoil energy

Journal Article · Tue Dec 27 00:00:00 EST 2016 · Physical Review D

DOI:https://doi.org/10.1103/PhysRevD.94.115026· OSTI ID:1331122

Bramante, Joseph ^[1]; Fox, Patrick J. ^[2]; Kribs, Graham D. ^[3]; Martin, Adam ^[1]

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1. Univ. of Notre Dame, Notre Dame, IN (United States)
2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
3. Univ. of Oregon, Eugene, OR (United States)

There exist well-motivated models of particle dark matter which predominantly scatter inelastically off nuclei in direct detection experiments. This inelastic transition causes the dark matter to upscatter in terrestrial experiments into an excited state up to 550 keV heavier than the dark matter itself. An inelastic transition of this size is highly suppressed by both kinematics and nuclear form factors. In this paper, we extend previous studies of inelastic dark matter to determine the present bounds on the scattering cross section and the prospects for improvements in sensitivity. Three scenarios provide illustrative examples: nearly pure Higgsino supersymmetric dark matter, magnetic inelastic dark matter, and inelastic models with dark photon exchange. We determine the elastic scattering rate (through loop diagrams involving the heavy state) as well as verify that exothermic transitions are negligible (in the parameter space we consider). Presently, the strongest bounds on the cross section are from xenon at LUX-PandaX (when the mass splitting δ≲160 keV), iodine at PICO (when 160≲δ≲300 keV), and tungsten at CRESST (when δ≳300 keV). Amusingly, once δ≳200 keV, weak scale (and larger) dark matter–nucleon scattering cross sections are allowed. The relative competitiveness of these diverse experiments is governed by the upper bound on the recoil energies employed by each experiment, as well as strong sensitivity to the mass of the heaviest element in the detector. Several implications, including sizable recoil energy-dependent annual modulation and improvements for future experiments, are discussed. We show that the xenon experiments can improve on the PICO results, if they were to analyze their existing data over a larger range of recoil energies, i.e., 20–500 keV Intriguingly, CRESST has reported several events in the recoil energy range 45–100 keV that, if interpreted as dark matter scattering, is compatible with δ~200 keV and an approximately weak scale cross section. Here, future data from PICO and CRESST can test this speculation, while xenon experiments could verify or refute this upon analyzing their higher energy recoil data.

• Research Organization: Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Univ. of Oregon, Eugene, OR (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: AC02-07CH11359; SC0011640
• OSTI ID: 1331122
• Alternate ID(s): OSTI ID: 1338116; OSTI ID: 1601474
• Report Number(s): FERMILAB-PUB-16-301-T; arXiv:1608.02662; PRVDAQ; 1480187
• Journal Information: Physical Review D, Vol. 94, Issue 11; ISSN 2470-0010
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS