[Paper Review] The Experimental Limits on Q-ball Flux with the Baikal Deep Underwater Array "Gyrlyanda"

И. А. Белолаптиков, L. Bezrukov+11 more|arXiv (Cornell University)|Feb 17, 1998

Aquatic and Environmental Studies3 citations

TL;DR

This paper establishes an upper limit on the flux of electrically neutral Q-balls (SENS type) by reanalyzing monopole flux limits from the Baikal Gyrlyanda deep underwater Cherenkov array, which operated from 1984 to 1990 with 267 days of live time. The study leverages the similarity in Cherenkov light signatures between SENS Q-balls and magnetic monopoles catalyzing baryon decay, resulting in a 90% confidence level flux limit of 3.9 × 10⁻¹⁶ cm⁻² sr⁻¹ s⁻¹ for Q-balls with nucleon absorption cross-section > 1.9 × 10⁻²² cm².

ABSTRACT

Supersymmetric models allow for stable non-topological solitons, Q-balls, which can be produced in the early Universe and contribute to dark matter. Experimental signature of electrically neutral Q-balls is, in fact, the same as is expected for superheavy magnetic monopoles catalyzing baryon decay. Here we use the upper limits on monopole flux obtained with deep underwater Cherenkov array "Gyrlyanda" which operated in the Baikal lake in 1984-90 with 267 days of live time to obtain the limit on Q-ball flux. The last has been found to be equal to 3.9 x 10^{-16} cm^{-2} sr^{-1} s^{-1} (90% CL). This result is discussed and compared with other restrictions.

Motivation & Objective

• .
• To derive a flux limit for electrically neutral Q-balls (SENS type) using existing monopole search data from the Gyrlyanda array.
• To compare the derived Q-ball flux limit with theoretical constraints from galactic dark matter density and other experimental limits.
• To assess the sensitivity of underwater Cherenkov detectors to Q-balls and identify future improvements via next-generation detectors like NT-200.

Proposed method

• .
• Reused monopole flux upper limits from the Gyrlyanda experiment (1984–1990, 267 days live time) to infer constraints on Q-ball flux.
• Assumed identical Cherenkov light production mechanisms between SENS Q-balls and monopoles catalyzing baryon decay.
• Applied the nucleon absorption cross-section formula σ ∼ 10⁻³³ Q¹/² (1 TeV/m)² to estimate detectable Q-ball interactions.
• Calculated effective detection area based on water optical properties and Cherenkov light yield, enabling flux limit derivation.
• Compared the derived limit with theoretical dark matter density constraints and other experimental limits from Baksan, IMB, Kamiokande, and MACRO.

Experimental results

Research questions

• RQ1 .
• RQ2 What is the upper limit on the flux of electrically neutral Q-balls (SENS type) based on the Gyrlyanda monopole search data?
• RQ3 How does the Q-ball flux limit compare with theoretical constraints from galactic dark matter density?
• RQ4 What is the sensitivity of underwater Cherenkov arrays to Q-balls, and how does it scale with detector size and efficiency?
• RQ5 Can future detectors like NT-200 improve upon the current flux limit for SENS Q-balls?

Key findings

• .
• The upper limit on the flux of SENS Q-balls is 3.9 × 10⁻¹⁶ cm⁻² sr⁻¹ s⁻¹ at 90% confidence level, derived from Gyrlyanda monopole data.
• The limit is valid for Q-balls with nucleon absorption cross-section > 1.9 × 10⁻²² cm².
• For m = 0.1 TeV, the limit applies for Q > 3.6 × 10¹⁸; for m = 100 TeV, it applies for Q > 3.6 × 10³⁰.
• The Gyrlyanda limit lies below the galactic dark matter density constraint only for a narrow range of Q and small m values.
• The Baksan telescope provides a stronger limit (4 × 10⁻¹⁹ cm⁻² sr⁻¹ s⁻¹) for SECS-type Q-balls, but this is not yet confirmed for SENS.
• Future detectors like NT-200 are expected to improve the flux limit by one to two orders of magnitude due to larger effective area and better electronics.