[Paper Review] TITUS: the Tokai Intermediate Tank for the Unoscillated Spectrum

C. Andreopoulos, Fct Barbato+76 more|arXiv (Cornell University)|Jun 27, 2016

Dark Matter and Cosmic Phenomena32 references5 citations

TL;DR

TITUS proposes a 2-ton Gd-doped water Cherenkov detector near Hyper-Kamiokande to enhance CP violation sensitivity and probe dark matter via vector-portal models. It leverages off-axis geometry to capture high-energy dark matter beams, with projected sensitivities of ~10⁻⁴⁰ cm² for 300 MeV WIMPs and 5×10⁻³⁹ cm² for 100 MeV WIMPs from indirect production.

ABSTRACT

The TITUS, Tokai Intermediate Tank for Unoscillated Spectrum, detector, is a proposed Gd-doped Water Cherenkov tank with a magnetised muon range detector downstream. It is located at J-PARC at about 2 km from the neutrino target and it is proposed as a potential near detector for the Hyper-Kamiokande experiment. Assuming a beam power of 1.3 MW and 27.05 x 10^{21} protons-on-target the sensitivity to CP and mixing parameters achieved by Hyper-Kamiokande with TITUS as a near detector is presented. Also, the potential of the detector for cross sections and Standard Model parameter determination, supernova neutrino and dark matter are shown.

Motivation & Objective

• Improve CP violation sensitivity in Hyper-Kamiokande by deploying a near detector with enhanced precision.
• Address the challenge of systematic uncertainties in oscillation measurements by utilizing a dedicated near detector with high granularity.
• Explore non-oscillation physics, including dark matter detection via vector-portal models.
• Enable high-sensitivity measurements of WIMP-nucleon scattering cross sections for low-mass dark matter.
• Leverage off-axis geometry and timing resolution to distinguish dark matter signals from neutrino backgrounds.

Proposed method

• Utilize a 2-ton Gd-doped water Cherenkov detector (TITUS) located ~2 km from the beam target to detect neutrinos and dark matter.
• Apply off-axis alignment to maximize flux of dark matter particles produced via direct and indirect processes involving vector mediators.
• Model dark matter production through two channels: direct $pp(n)\rightarrow V^{*}\rightarrow\bar{\chi}\chi$ and indirect $pp(n)\rightarrow\phi+...\rightarrow V+...\rightarrow\bar{\chi}\chi$.
• Exploit kinematic features such as high-energy cutoffs and cusp structures near kinematic limits to distinguish dark matter from neutrino backgrounds.
• Use LAPPDs to enhance time resolution and distinguish dark matter timing signatures from neutrino beam pulses.
• Apply the VaLOR fitting method to assess CP violation sensitivity under realistic systematic uncertainties.

Experimental results

Research questions

• RQ1 Can TITUS achieve 5σ sensitivity to CP violation across a significant fraction of δcp parameter space?
• RQ2 How does off-axis geometry enhance the detection of dark matter beams from vector-portal models?
• RQ3 What is the projected sensitivity of TITUS to WIMP-nucleon scattering cross sections for low-mass WIMPs?
• RQ4 Can kinematic features such as cusp structures at high momentum transfer distinguish dark matter from neutrino backgrounds?
• RQ5 To what extent can timing resolution from LAPPDs improve signal identification in dark matter detection?

Key findings

• TITUS can achieve 5σ sensitivity to CP violation for 62% of the δcp parameter space using a 1.3 MW beam and 1:3 ν-mode to ḡν-mode ratio.
• The detector can provide a 3σ measurement of CP violation for 79% of δcp space, approaching the 84% achievable without systematic uncertainties.
• For dark matter detection, TITUS achieves a projected sensitivity of ~10⁻⁴⁰ cm² for 300 MeV WIMPs via direct production.
• For 100 MeV WIMPs, the sensitivity reaches 5×10⁻³⁹ cm² via indirect production, assuming mediator mass between 1 GeV and 400 GeV.
• Kinematic cusp features near the beam energy limit provide a distinctive signature for dark matter, especially in off-axis configurations.
• The use of LAPPDs enhances time resolution, enabling discrimination of dark matter production timing from neutrino beam pulses.