1. VHMPD proto-collaboration
Very High Momentum Particle Identification Detector for ALICE at the LHC Nikolai Smirnov, Yale University for the VHMPID proto-collaboration
Abstract
We propose the construction of a detector to extend the capabilities of ALICE in the high transverse momentum pT region. The proposed VHMPID detector performs charged hadron identification on a track-by-track basis in the 10 GeV/c < pT < 25 ( Option 1) or 35 ( Option 2) GeV/c momentum range and provides ALICE with new opportunities to study parton-medium interactions at LHC energies. The VHMPID covers 8% of the TPC acceptance and presents sufficient acceptance for triggered- and tagged-jet studies, allowing for the first time identified charged hadron measurements in jets. There are two special constrains on the VHMPID in ALICE: a 1.2 m maximum radial distance available, and the necessity to trigger on high pT charged particles.
Detector Geometry and Components
Double Cherenkov Radiator, Option 2
Focusing RICH, CF4 gas radiator ,spherical mirror and GEM Detector with CsI (windowless approach)
Tracking Detector
Threshold Cherenkov Detector (TIC mode), C4F10 gas radiator, quartz window and GEM Detector with CsI
Each detector read-out – pads 0.5x0.5 cm2
This option provides its own “high pT” trigger
Coverage ~ 8 % of TPC acceptance in phase space
BACKFRAME
PHOS
VHMPID
Identification momentum range
Full scale simulation and reconstruction including CF4 scintillations
π and p identification probability with Central Pb+Pb HJ as a background
Possible position in ALICE with modules of 1.4x1.0x1.10 m3
signal
Absence of signal π
3 - 35 K
9 - 35 p
9 - 18
Detector Geometry and Components ( Option 1 )
Radiator gas C4F10 (n ≈ , gth ≈ 18.9).
Quartz window
Photon detectors Pad-segmented CsI photocathode is combined with a MWPC with the same structure and characteristic of that used in the HMPID detector. The gas used is CH4, the pad size is 0.8×0.84 cm2 (wire pitch 4.2 mm), or a GEM-like detector with a CsI photocathode (higher gain, feedback photons suppression). Focusing RICH - spherical mirror with the detector at R/2.
This option needs 3-4 additional tracking detectors for a “high pT trigger”
P, GeV/c
P, GeV/c
Particle was identified as π (Blue), k - Red, p – Green, No PID - black
Detector response ( cluster charge) for UV photons and MIPs and High pT trigger possibility
Cluster charge, pC
Three reconstructed MIP hits were
matched as a track,
Line fit in (XY) and (RZ)
DCA to (0., 0.) in (XY), cm
DCA, cm
With cuts selected to get 98% efficiency for “one high Pt track / event”
for Central HIJING event the probability to get a false trigger
( “DCAxy < 15. cm”) is smaller than 4% / detector
Simulations
Full simulation in AliRoot (or/and “stand-alone” using GEANT-3 + reconstruction),
Hough transform has been applied to separate signal from background.
One pion track is embedded in a 5.5 TeV Pb+Pb HJ event with a charged particle multiplicity dNch/dy ~ 4000 at midrapidity. Pion trace is clearly detected in the MWPC above the background .
Pt, GeV/c
Blue – UV photons; Red – MIPs
Green – No FEE Noise
VHMPID
There are two more topics to be discussed:
I ) ALICE EMC as a trigger for VHMPID
II ) ALICE TPC PiD performance on track-by-track basis
The absolute scintillation light yield of CF4 was measured using a CsI photocathode GEM
Identification momentum range
9 – 18 GeV/c
18 – 24 GeV/c p
9 – 14 GeV/c
3 -14 GeV/c
Absence of signal
signal k
Scintillation Yield = ± 9.8 g / MeV
Preliminary results reported:
B.Azmoun et.al., Conf. Rec IEEE NSS/MIC
A.Pansky et.al., Nucl. Inst. Meth. A354 (1995)
Y= 250 ± 50 g/MeV with PMT
Variable distance between Am source and SBD
Variable distance between light source and GEM
3s separation , 80 cm long radiator
Conclusion:
A VHMPID of about 9 square meters with identification of protons track by track up to GeV/c is technically possible. Positioned opposite to the EMCAL in ALICE it would allow the study of jets with a gamma in the EMCAL and would give about 1000 events up to 30GeV. For dijets an annual yield of events would reach 120 GeV.
π and p identification probability with Central Pb+Pb HJ as a background
VHMPD proto-collaboration
A.Agócs3, R. Alfaro4, G.Barnafoöldi, L. Boldizsár3, E. Cuautle1, G. De Cataldo2,6, D. Di Bari2, A. Di Mauro6, Z. Fodor3, F. Formenti6, E. Futó3, E. García5, J. W.Harris7, G. Hamar3, P. Lévai3, P. Martinengo6, A. Mastroserio2, L. Molnár2,3, E. Nappi3, A. Ortiz1, D. Perini6, V. Peskov1, F. Piuz6, P. Podesta1, L. Serkin2, O. Sokolov1, N. Smirnov7, D. Varga3, G. Volpe3
1Instituto de Ciencias Nucleares Universidad Nacional Autónoma de México
2Dipartimento di Fisica dell’Università degli Studi di Bari and INFN Sezione di Bari, Bari, Italy
3MTA KFKI RMKI Research Institute for Particle and Nuclear Physics
4Instituto de Física, Universidad Nacional Autónoma de México
5Chicago State University
6CERN
7Yale University
P, GeV/c
P, GeV/c
This work has been supported by the projects Conacyt 44268F and , DGAPA –UNAM IN , OTKA No NK062044, IN71374, DoE DE-FG02-94ER
Particle was identified as π (Blue), k - Red, p – Green, No PID - black