CNGS beam monitor with LVD G. Sartorelli M. Selvi Bologna University and INFN
The CNGS beam The CNGS beam provides about 2600 CC/kt/year at nominal beam intensity at the Gran Sasso Labs. CERN-SL-2000-063EA and CERN-SL-2001-016EA A.E.Ball et al. propose to build a large area En (GeV) muon monitor at GS
Why a monitor at LNGS?
Why a monitor at LNGS?
Large Volume Detector 3 2 CNGS beam 1
Large Volume Detector 3 identical towers in the detector 35 active modules in a tower 8 counters in one module
Large Volume Detector
Large Volume Detector Front area: ~ 13 m x 11 m
Event Generation n * m m LVD CNGS beam Gran Sasso rock Interaction kinematics with LIPARI code Muon transport in rock with MUSIC LVD detector simulation with GEANT
m energy spectrum Em (GeV) Em (GeV)
m angular distribution Muon angle, with respect to the hall A axis, is due to: Beam angle (3.2 o ) CC interaction (4.8 o ) Path in rock (1.6 o ) Total mean angle in space: 6.2 o
Event Display: m from rock
Counter Multiplicity In 79% of the events hitting the LVD mother volume at least one scintillation counter is fired. (geometrical efficiency: e G ) 21% does not hit any sensitive volume
Event Display: m from rock
m tagging Em released per counter > 200 MeV Detection efficiency e D ~ 92% Global efficiency = geometrical x detection = 79% x 92% = 72%
Number of m from the rock Rock Mass Nominal CNGS intensity CC interaction rate n m CC in rock Number of m in LVD mother volume LVD geometric efficiency LVD global efficiency Detected m in LVD 1969 ktons 4.5 x 10 19 pot/year 5.85 x 10-17 CC/pot/year 5.18 x 10 6 / year 33600 / year 79% 72% ~ 120 / day
Event Display: internal n CC * Interaction vertex En = 26.1 GeV Em = 5.6 GeV E released = 8.7 GeV Missing E h = 6.8 GeV Missing Em = 3.6 GeV Missing E IRON = 7.0 GeV
Event Display: internal n NC Interaction vertex En = 19.5 GeV E released = 9.8 GeV Missing E h = 1.6 GeV Missing E IRON = 8.1 GeV
Number of internal n events Scintillator Mass Steel Mass (tank and portatank) n m CC in LVD n m NC in LVD selection efficiency Detected internal events in LVD 1044 tons 770 tons 4770 / year 1460 / year 97% (CC) 91% (NC) ~ 30 / day
Total number of CNGS events Detected muons from the rock Detected internal events in LVD Detected CNGS events in LVD (rock muons + internal neutrinos) ~ 120 / day ~ 30 / day ~ 150 / day
Background Estimate The main background sources are cosmic muons. The rate in the full LVD detector (3 towers) is 9300 muons/day (6.5 per minute). Requiring the same cut used to tag muons (an energy loss greater than 200 MeV per scintillation counter), 75% of them survive. Too many! The use of the informations from the CNGS beam spill (10.5 ms of spill lenght and 50 ms inter-spill gap*) allows a reduction of the number of cosmic muons of a factor 10 4, about 1.5 cosmic muons per day. LVD time resolution: 12.5 ns The cosmic muons background is negligible!
A different detector... RPC wall or LST or... m 1 m 1 m 13x13 m 2 148 m/day as in CERN-SL-2001-016EA 13 x 14.5 m2 (the largest area in the biggest hall C) 166 m/day 8x9 m 2 (OPERA spectrometer) 65 m/day + ~30 contained event/day.
Conclusions CERN-SL-2001-016 EA:... Large area muon monitoring planes at Gran Sasso are suggested which would detect muons induced by neutrino interactions in the rock upstream of the experimental caverns LVD fulfills the requirement for the CNGS beam monitor, allowing ~120 detected muons per day + an additional number of ~30 internal n interactions (CC+NC): no need for a dedicated muon monitor (at least in hall A) 3% statistical error in 7 days