Searches for decays of new particles in the DUNE Multi-Purpose near Detector

Abstract

One proposed component of the upcoming Deep Underground Neutrino Experiment (DUNE) near detector complex is a multi-purpose, magnetized, gaseous argon time projection chamber: the Multi-Purpose Detector (MPD). We explore the new-physics potential of the MPD, focusing on scenarios in which the MPD is significantly more sensitive to new physics than a liquid argon detector, specifically searches for semi-long-lived particles that are produced in/near the beam target and decay in the MPD. The specific physics possibilities studied are searches for dark vector bosons mixing kinetically with the Standard Model hypercharge group, leptophilic vector bosons, dark scalars mixing with the Standard Model Higgs boson, and heavy neutral leptons that mix with the Standard Model neutrinos. We demonstrate that the MPD can extend existing bounds in most of these scenarios. We illustrate how the ability of the MPD to measure the momentum and charge of the final state particles leads to these bounds. arXiv:1912.07622v1 [hep-ph] 16 Dec 2019 Liquid Argon Near Detector: The liquid argon near detector has a width (transverse to the beam direction) of 7 m, a height of 3 m, and a length (in the beam direction) of 5 m. The fiducial mass of the near detector is 50 t of argon. See Ref. [2] for more detail.Multi-Purpose Detector: The Multi-Purpose Detector (MPD) is a magnetic spectrometer with a cylindrical high-pressure gaseous argon time projection chamber (HPTPC) at its heart. The HPTPC has a diameter of 5 m and a length of 5 m. It is surrounded by an electromagnetic calorimeter (ECAL) and the HPTPC+ECAL system is situated inside a magnet with 0.5 T central field. The axis of the cylinder is perpendicular to the beam direction. However, for simplicity, when simulating our signals (see Section 3), * Some projections of DUNE operation include the possibility of an upgraded beam (roughly twice the number of protons on target per year) that can operate in the second half of the experiment. We assume a constant number of protons on target per year, so our ten-year projection is equivalent to a shorter operation time with such an upgraded beam. † This is in contrast with the LArTPC, where the conversion distance of photons is O(10 cm). Far more photons can fake the signal of e + e − in the LArTPC than in the HPTPC. * Ref. [63] provides a thorough review of searches for dark photons and existing constraints. * The results of this analysis in antineutrino mode are qualitatively equivalent.

GeV-scale neutrinos: interactions with mesons and DUNE sensitivity

“…At low masses the heavy neutrino production is dominated by pion decay, which is roughly proportional to |U α4 4 , as expected. We have also compared our results to similar studies in the literature [53,54,56], after the corresponding rescaling of the number of events accounting for the different detector volumes, PoT and efficiencies assumed, we find a rather good agreement between the four estimations of the DUNE sensitivity. We find the best overall agreement with Ref.…”

“…For intermediate HNL masses M, between the MeV and GeV scales, searches at beam dump experiments or near detectors of neutrino oscillation facilities, where they can be produced via meson decays and detected through their visible decays, can set very stringent constraints [14,28,[49][50][51][52][53][54][55][56][57][58][59][60][61][62]. Indeed, current bounds are even getting near the expectation for the "vanilla" type-I Seesaw without a lepton number symmetry protection of the light neutrino masses m ν , where the mixing scales as θ 2 ∼ m ν /M.…”

“…As an application of our framework, we compute the expected flux of HNLs at the proposed DUNE [53,54] near detector, and compare our full numerical simulation with the approximation of rescaling the massless neutrino fluxes. A significant enhancement due to the larger boost in the beam direction for the HNLs is found.…”

Neutrino masses and Hubble tension via a Majoron in MFV

“…2, the heavy neutrino masses lie in ranges that may lead to detection in various experimental facilities. Neutrinos with masses ranging from tens to hundreds of MeV can be probed for and be potentially detected at beam dump or even near detectors of neutrino oscillation experiments [111][112][113][114][115][116][117][118], such as DUNE or SHiP, whereas those with masses in the range of tens to hundreds of GeV have interesting prospects of being produced at the LHC or future colliders [112,[119][120][121][122][123][124][125]. On the other hand, given their extremely small couplings, the heavy neutrinos produced in the early Universe would not be Boltzmann suppressed when decoupled from the thermal bath, leading to an unacceptably large contribution to the relativistic degrees of freedom of the Universe after their subsequent decay [126][127][128][129][130].…”

Pair production of dark particles in meson decays

“…NuCal is expected to set somewhat more stringent lower limits on our parameter space than CHARM [73], but by a factor smaller than 2. Future experiments such as SHiP [74,75] and DUNE [76,77] can provide an intense source of η mesons where the subsequent decay of X 2 may be searched for. Moreover, the models presented here can also be probed via collider production of η mesons with largest attainable boosts.…”