El disparo de rayos c

1
The ALICE Cosmic Ray Trigger E. Casimiro, A.
Fernández, E. Gámez, R. López, S. Román, L.
Villaseñor, A. Zepeda Depto. de Física
CINVESTAV-IPN Benemérita Universidad Autónoma
de Puebla Universidad Michoacana de San Nicolás
de Hidalgo
Introduction In recent decades, cosmic ray
air showers initiated by high-energy proton or
nucleus collisions in the atmosphere have been
studied with large area experiments on the
surface or with muon measurements deep
underground. In principle, these cosmic ray
experiments explore two completely different
realms of physics, particle astrophysics and
particle interaction physics, which are, however,
intimately related by the interpretation of the
data. Several groups at CERN have proposed
to use their detectors and underground area
facilities to study cosmic rays, e.g. UA1ua1
and more recently by the LEP experiments 2
(ALEPH, L3 and DELPHI). The ACORDE-ALICE
group have proposed to install an array of
scintillator counters on top of the ALICE magnet
at P2-LHC cavern 40 m underground, together with
a 150 x 150 m2 array of scintillation counters
arranged on a 10 m grid on the surface above
P2.The simultaneous and complementary measurement
of the muonic and the electromagnetic component
of a cosmic ray air shower with this apparatus
could provide the determination of both shower
core and primary energy by two independent
methods.
ALICE Detector
Large Hadron Collider CERN
ALICE at point 2
ACORDE
HMPID
TRD
PMD
TPC
MUON SPEC.
ITS
TOF
PHOS
FMD
The ALICE Collaboration is building a dedicated
heavy-ion detector to exploit the unique physics
potential of nucleus-nucleus interactions at LHC
energies. The main purpose is to study the
physics of strongly interacting matter at extreme
energy densities, where the formation of a new
phase of matter, the quark-gluon plasma, is
expected.

• Astroparticle physics
• Energy spectrum, chemical composition
• Acceleration mechanism, anisotropy
• Exotic events
• (muon bundles, centauro, anti-centauro, etc.)
• Particle interactions physics
• forward particle production
• p-p, p-A interactions
• Heavy quark production

ALICE TPC (Time Projection chamber)
The detector ACORDE Acorde-1 Acorde-2
Acorde-1 Array of scintillator counters on top
of ALICE Magnet combined with Alice tracking
detectors (TPC, TOF, HMPID) UNANIMOUSLY
ACCEPTED (March 20th 2002) Acorde-2 Array of
scintillator counters at the surface of the LCH
Point 2 (Under consideration)
The ALICE TPC is the main tracking detector of
the central barrel and together with the inner
tracking detectors has to provide charged
particle momentum measurement, particle
identification and vertex determination with
sufficient momentum resolution two track
separation and dE/dx resolution for studies of
hadronic and leptonic signals in the region pt lt
10 GeV/c and pseudorapidities -0.9 lt ? lt 0.9. In
addition we plan, to use the TPC to reconstruct
cosmic ray events with a very high multiplicity

p p Physics related to cosmic ray at LHC central
rapidity
ACORDE scintillators modules
Scintillator Array
Cosmo-Aleph TPC (lateral view)
Muon bundles ALEPH detected some (very
intriguing) events with high multiplicity, up to
160 tracks reconstructed at their TPC central
region
Cosmic ray flux at the ALICE cavern. ALIROOT
simulation
To detect cosmic rays in ALICE a tool, named
ACORDE (Alice Cosmic Ray Detector), has been
proposed 4. This device will provide a fast
level-zero trigger signal to the central trigger
processor, when cosmic ray particles impinge upon
the ALICE detector. To implement this trigger we
will locate panels of plastic scintillator
counters above the three upper faces of the ALICE
magnet. Each panel contains 16 counters arranged
in 8 rows of doublets. Each doublet consists of
two parallel (side by side) counters. We have
arrived to a preliminary design of the
geometrical arrangement of the scintillator
panels covering the top magnet face in which will
collocate four panels (covering the central part
of the top face) arranged transversely (i.e. with
the counters running transverse to the larger
side of the face). The two magnet faces just on
the sides of the top one can be covered
similarly. Depending on physics issues we may
decide to cover more area of the upper faces of
the ALICE magnet. The cosmic ray trigger has to
deliver (to the central trigger processor) a
level-zero signal, indicating a cosmic ray
event, within a 850 nsec window from the crossing
of a particle through our detectors. A base line
implementation shall require coincidences (within
a certain time window) between two counters on a
doublet. If any coincidence occurs, it will
generate a short pulse and AND-it to the LHC
Clock. The resulting output will be our trigger
signal.
L3C Experiment
By the end of LEP operation, L3 experiment made
an special cosmic ray run. A high precision
momentum and µ/µ- ratio spectrum (30 GeV 1 TeV
range), was obtained 3.

• References
• O.C. Allkofer, K. Eggert, P. Erhard et al. The
  UA1 detector as a possible cosmic ray device,
  Proc. 17th Int. Cosmic Ray Conf.,Paris, 10 (1981)
  
• CosmoLep, an underground cosmic ray muon
  experiment in the LEP ring, CERN/LEPC 99-5,
  LEPC/P9
• P. Le Coultre, L3C collaboration, Proceedings of
  the 27th Int. Cosmic Ray Conf., Hamburg, Germany,
  Vol. 7, p305.
• http//elinares.home.cern.ch/ACORDE/index.html

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