A Search for Massive Magnetic Monopoles at the Baksan Underground Scintillation Telescope

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A Search for Massive Magnetic Monopoles at the
BaksanUnderground Scintillation Telescope

• Yu.F. Novoseltsev, M.M. Boliev, A.V. Butkevich,
  S.P.Mikheev, V.B. Petkov

Institute for Nuclear Research of RAS
Pylos - 2004
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The experiment has been performed for both fast
(ß 0.4) and slow (210-4 ß 10-1)
monopoles. In the velocity range ß 0.4, we made
use of "the cascade trigger" (large energy
deposition in the facility), the time-flight
method was used for 210-4 ß 10-1
range. BUST is located at the depth of 850 m
w.e. The facility dimensions are
171711 m3.

• The slow trigger requires
• of internal plane operation
• SO 1850 m2sr
• (isotropic flux)
• The ß 0.4 trigger requires
• crossing of three horizontal
• planes
• SO 728 m2sr
• (isotropic flux)

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2?10-4 lt ß lt 0.1

• in 1 means
• 6 external planes
• in 2 is 2 internal
• planes
• Trigger rate is
• 200 per day

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• Trigger is the coincidence of the signal from
  one of
• external planes with the internal plane
  signal delayed
• greater than 50 ns.
• Live time 127630 hours 14.56 years
• (01.1982 - 01.2000)
• Only events with three hit planes were considered
  as slow particle candidates (because a background
  from stopping of muons with subsequent µ - e
  decay was rather large)

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• All triggered events can be subdivided into 3
  groups
• 44 - µ-e decays
• 54.6 - random coincidence
• 1.4 - relativistic muons which have flight time
  gt 50 ns
• (large zenith angles ? 80o)

No candidate for the slow particles was recorded
FMM 3.2 10-16 cm-2s-1sr-1 (90 CL)
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ß 0.4, q 137/2e

• The events were selected in which the energy
  deposition in
• the facility exceeded eth 1540 r.p. 77
  GeV
• (1 r.p. 50 MeV)
• To estimate the light yield (dL/dx) in a
  scintillator we use
• the expression (Salamon, Ahlen, 1981)

(1)
where dE/dx is the total energy loss, A 0.03,
B is the quenching parameter, F is the fraction
of energy loss which results from excitations
outsite the core.
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Some characteristics of BUST and MACRO
scintillators
BUST scintillator MACRO scintillator
density, g/cm3 0.78 0.86
H/C ratio 2.1 2.02

• In passing of MM through the BUST, the energy
  deposition
• e gt eth/4 385 r.p. should be observed in
  each of planes intersected by MM (this value
  (eth/4) determines the least
• velocity of MM (ß 0.4))
• The energy deposition have to be the undamped one
  
• in contrast to the cascade

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ß 0.4

• Live time 35400 hours

• No candidate for the undamped energy deposition
  was obtained

FMM 2.5 10-15 cm-2s-1sr-1 (90 CL)
Pylos - 2004
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Pylos - 2004