Detection of muons in PHENIX (& ALICE)

Kyle Schmoll

University of Tennessee

04/18/12

   

Outline● Why Muons?

muon properties

what can we learn?

simulation

● Muon Detection in PHENIXtracking

identification

● Differences in ALICEtracking

identification

   

Muon Properties

● Same charge as electron, mμ = 105.658 MeV

● Lifetime:     = 2.2 μs τ

● mμ >> m

e and long lifetime   small crosssection→

● Live long enough to be detected● Easy to discriminate from electrons and hadrons

   

What can we learn?● Study J/  production using ψ

J/    μψ → +μ (5.93%)● Measure cross section of 

open heavy flavor using     D

0   → Kμ+ν

μ , etc (17.6%)

● Can also look at stopped hadrons in muon arms

   

Momentum Correlation

   

Angular Correlation

● Magnitude of pt is not 

strongly correlated

● Direction of pt in lab 

frame is● Due to relatively low 

mass of muon

mμ 

   

Muon Detection in PHENIX

   

Tracking (CSC)● Cathode strip chamber in magnetic field● Passage of muon produces ionization

● Anode collects charge ● Induced charge 

distribution on cathode

● Cathodes are read out● Fit signal to determine 

position

   

Tracking (PHENIX)● 3 stations● 3 gaps per station● Gap consists of cathode 

anode sandwich● Gaps seperated into 

octants

   

Specs● Copper coating used for cathode plane● Gold plated CuBe wires for anodes with 1 cm 

spacing

● 104 X0 allows for low multiple scattering

● Operated with 50:30:20 mix of Ar:CO2:CF

4 at a 

bias of 1.71.85kV● Fitting signal to Mathiason function determines 

position to high accuracy (~130 μm)

   

Mathiason fit

● Resolution ~ 130 μm

   

Magnet

● Used for momentum measurement

● Composed of iron piston

● Asymetric to accomodate asymetric muon arm

   

Muon Tracking Readout● ~ 21,000 cathode strips readout through Front End 

Electronics (FEE)● Signal from cathode connected to Cathode 

Preamplifier (CPA) of a Cathode ReadOut Card (CROC)

● CROC stores signal in Analog Memory Unit/Analog to Digital Converter (AMUADC)

● This combination is Front End Module (FEM)● South arm utilizes 168 FEMs

   

MuTr Readout

   

Identification (PHENIX)● Absorbers used to stop 

hadrons● Streamer tubes used to 

reconstruct tracks● Cuts on data made 

accordingly

   

Absorber● Total absorber is ~1.5 m of steel

● ΛI ~ 16 cm in steel for pions

● 1  e3.75 = 97.6% rejected before tracker● 99.99% rejected by

gap 4

●  π →μνμ (99.98%) 

contributes to

background

   

Iarocci streamer tubes

● Used for track reconstruction for event rejection

● Graphite coated inside of tube forms cathode● 100 μm gold plated CuBe wire is anode● Particles produce ionization which is collected on 

anode

● Operated with 91.5% CO2 8.5% isobutane at 4.5 kV 

(proportional mode)

   

MuID Readout● Amplified signal is 250 mV● 30 m twistedpair cables to FEE● ROC digitizes signal into 0 or 1 (hit/no hit)

   

Differences in ALICE

   

ALICE● ALICE uses the same concept as PHENIX with 

different detector technology● Momentum measurement first● Track ID after

● Only 1 muon arm!!!

   

Tracking in ALICE● Cathode Pad Chambers instead of Cathode Strip Chambers

● Readout a million channels at order of kHz

● 16channel Multiplexed ANAlogic Signal (MANAS) chip used as:

amplifier

shaper

filter

● Digitized on board, read by Muon Arm Readout Chip (MARC)

● This chain is mounted on front end boards (MANU)

● 17,000 MANU's needed to readout 1.08 million channels

● 5 stations instead of 3

   

Identification in ALICE● Resistive Plate Chambers (RPC) used instead of 

drift tubes● Trigger detector consists of 4 RPC planes in 2 

stations● Track resolution ~ 1 cm (better than PHENIX)● Signal sent through discriminator to trigger 

electronics which reconstruct track based on info from 4 planes

   

Sources● A. M. Glenn, Single Muon Production and Implications for 

Charm in 200 GeV Au+Au Collisions, PhD thesis, University of Tennessee, 2004.

● D. Hornback, A measurement of open charm using single muons at forawrd angles for p+p collisions at center of mass energy 200 GeV, PhD thesis, University of Tennesse, 2009.

● The ALICE collaboration et al, The ALICE experiment at the CERN LHC, 2008 JINST 3 S08002.

● The ALICE collaboration et al, Heavy flavour decay muon production at forward rapidity in protonproton collisions at √s = 7 TeV, Phys. Lett. B 708 (2012) 265.

# 35L35.pdfP627 YK4/18/2012

Average abundance ratio Dark Natter / Ordinary Matter  6

http://en.wikipedia.org/wiki/Dark_matter

Galactic rotation curves

Gravitational lensing

Galaxy clustering and collisions

CMBR

Most popular for the last two decades was the hypothesis that DM consist of LSP (Lightest Super-Symmetric – stable particles). More generalized name: WIMPs (Weakly Interacting Massive Particles) is frequently used. In different models of super-symmetry breaking SUSY masses are parameters.

Generic features of SUSY models:colored particles are heavy; non-colored – light;neutralino is LSP;the overall scale is a free parameter.Neutralino is a Majorana fermion, mixture of photino, Zino, higgsino. Lightest stable neutralino is expected to have mass 80-120 GeVand be invisible at LHC (detected asmissing energy/mass)

• Cross section is ~ weak but unknown (model-predictable in SUSY)• Mass of target: (a) heavy to enhance

(b) optimum to maximize the energy transfer

( )24

(max) ; - mass of nucleus; M - mass of DM particlerecoil DM

mMT T m

m M= ⋅

+

2

Maximum of "maximum energy transfer":

0 4 ( ) 4 2( ) 0

( ) 2 0;

dTM m M mM m M

dm

m M m M m

= + - ⋅ + =

+ - = = T

Yukawa potential:dNdT

Coulomb-like potential:

2

1dNdT T

µ

“Velocity distribution of dark matter”Malcolm Fairbairn

Escape velocity of our galaxy lies within the range 498 km/s < vesc < 608 km/s (90 per cent confidence)RAVE Survey: http://arxiv.org/abs/astro-ph/0611671v2

131

2

2

2

E.g. 100 GeV scatters on 122 GeV

40.99 ;

( )

2

100 25035

2 300, 000

DM

DM

MXe

mM

m M

MT v

GeVKeV

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http://arxiv.org/abs/1109.0702

From Mariangela Lisanti / Princeton, BLV-2011 talk, September 2011, Gatlinburg TN

From Mariangela Lisanti / Princeton, BLV-2011 talk, September 2011, Gatlinburg TN

CoGeNT and DAMA/Libra observations

LHC implications for DM detection

SUSY paradigm might not work… Other possible DM paradigm is e.g. Mirror Matter (Z. Berezhiani…): DM consists of H, He, etc. light mirror nuclei.DAMA, CoGeNT, CRESST might see some “light DM”

If DM is light (M < 10 GeV) then target nuclei should be also light

2

Thermalized DM: 2Hm v

kT= =E

Light Dark Matter Detector

Gas detector filled with Hydrogen (or methane CH4) under high pressure.

A. H2 gas at 20C and 1 atm has =0.0838 g/l (compare with liquid is 0.0708 g/cm3)

Assume detector with length 1 m and diameter 0.8 mVolume V= 1042 liters 500 lAssume working pressure 50 atm, then density =4.2 g/lThen, fiducial mass is 2 kg.

B. Compare with DAMA/Libra; they have 250 kg of NaI where Na is 15.3%.So, the light nuclei (Na) mass in DAMA/Libra is 38.3 kg

C. Number of electronics channels is:With cell radius 2 cm 400 channels

D. Electrodes structure:

Prototype of such a detector - NA6 Experiment at CERN (ITEP-Freiburg Collab.)

55

2

source 5.9 KeVin ~ 40 atm H (HV 29 kV, gain ~600)A. Bamberger et al, NIM 156 (1978) 107-110

Fe

(a) High Pressure Proportional Counters Operating in Pure Hydrogen.A. Bamberger et al, Nucl.Instrum.Meth.156:107-110,1978.

(b) A Hydrogen High Pressure Proportional Drift Detector.A. Arefev et al, Nucl.Instrum.Meth.A224:75,1984.

(c) Measurement of n-p elastic scattering at high-energies and very small Momentum transfers., A. Arefev et al. Nucl.Phys.B232:365,1984.

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