Dark matter constraints on low mass and weakly coupled B−L gauge boson

Abstract

We investigate constraints on the new B − L gauge boson (Z BL) mass and coupling (g BL) in a Uð1Þ B−L extension of the standard model (SM) with an SM singlet Dirac fermion (ζ) as dark matter (DM). The DM particle ζ has an arbitrary B − L charge Q chosen to guarantee its stability. We focus on the small Z BL mass and small g BL regions of the model, and find new constraints for the cases where the DM relic abundance arises from thermal freeze-out as well as freeze-in mechanisms. In the thermal freeze-out case, the dark matter coupling is given by g ζ ≡ g BL Q ≃ 0.016 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi m ζ ½GeV p to reproduce the observed DM relic density and g BL ≥ 2.7 × 10 −8 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi m ζ ½GeV p for the DM particle to be in thermal equilibrium prior to freeze-out. Combined with the direct dark matter detection constraints and the indirect constraints from cosmic microwave background and AMS-02 measurements, discussed in earlier papers, we find that the allowed mass regions are limited to be m ζ ≳ 200 GeV and M Z BL ≳ 10 GeV. We then discuss the lower g BL values where the freeze-in scenario operates and find the following relic density constraints on parameters depending on the g BL range and dark matter mass: Case (A): for g BL ≥ 2.7 × 10 −8 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi m ζ ½GeV p , one has g 2 ζ g 2 BL þ 0.82 1.2 g 4 ζ ≃ 8.2 × 10 −24 ; and Case (B): for g BL < 2.7 × 10 −8 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi m ζ ½GeV p , there are two separate constraints depending on m ζ. Case (B1): for m ζ ≲ 2.5 TeV, we find g 2 ζ g 2 BL ≃ 8.2 × 10 −24 ð m ζ 2.5 TeV Þ; and Case (B2): for m ζ ≳ 2.5 TeV, we have g 2 ζ g 2 BL ≃ 8.2 × 10 −24. For this case, we display the various parameter regions of the model that can be probed by a variety of "Lifetime Frontier" experiments such as FASER, FASER2, Belle II, SHiP, and LDMX.

Unravelling the richness of dark sector by FASERν

“…• X is a gauge boson of mass of few 100 MeV-few 10 GeV associated with the anomaly free symmetry B − a e L e − a µ L µ − a τ L τ (with a e + a µ + a τ = 3) or a dark photon mixed with ordinary photons. Such possibilities are studied in [12,[14][15][16].…”

“…Refs. [13][14][15] consider a singlet scalar mixed with the SM Higgs. As a result, the effective coupling of this scalar to the heavier generations will be stronger and their main production mode at the LHC would be JHEP10(2020)008…”

“…The possibility to search for heavy neutral leptons has been considered, both when they arise from heavy meson decays [10,11] and in the presence of new B − L gauge interactions [12]. FASER sensitivity to dark matter particles and axions/dark photons, and their possible connections, has been explored within various scenarios [13][14][15].…”

Light, long-lived B − L gauge and Higgs bosons at the DUNE near detector

“…The U(1) B−L gauge symmetry is a well-motivated extension [1,2] of the Standard Model (SM), which provides a natural framework to account for the tiny neutrino masses via the type-I seesaw mechanism [3][4][5][6][7]. It may also accommodate a light dark matter (DM) particle which interacts with the SM particles through the scalar or gauge portal of U(1) B−L [8]. In this paper, we focus on the class of B − L extensions of SM, where B − L does not contribute to electric charge so that its gauge coupling g BL can be arbitrarily small making the associated gauge boson Z very light with mass in the sub-GeV range [9][10][11].…”

“…In this case, we can expect the corresponding U(1) B−L -breaking scalar (denoted here by ϕ) to be also light. Both Z and ϕ are essential ingredients of the U(1) B−L extension, and play important role in connecting DM to the SM, in DM phenomenology [8,[12][13][14][15][16][17], and in explaining the observed light neutrino masses [18][19][20][21][22][23][24]. Since the seesaw mechanism does not depend directly on the gauge coupling value, such low gauge coupling models can still accommodate the seesaw mechanism.…”