PHENIX Overview
Mickey Chiu
Brookhaven National Lab
VNI Simulations: Geiger, Longacre, Srivastava, nucl-th/9806102
In the Beginning…
•We want to create a quark gluon plasma and measure it’s properties
•System is about 10-100 fm big (10-14-10-13 m)
•System lasts for ~10-22 s (t ~ L/c where L ~ 10 fm)
•Collisions occur at rates of 10,000 (Au+Au) to 10,000,000 (p+p) times per second•Requires trigger and fast DAQ
•Produces hundreds of particles into your detector•Requires fine segmentation
•Like smashing two swiss watches at incredible speeds and looking at the broken up insides (from California) to figure out how the watch worked
…and a rough idea how things evolve
Pre-equilibrium
Thermalization
QGP phase
Mixed phase
Hadronization (Freeze-out) + Expansion
p K
e
Space (z)
Tim
e
Au Au
etc.. jet
e
“Passage of particles through matter”
http://pdg.lbl.gov
•Bethe-Bloch equations•Governs ionization loss of particles as they traverse through matter•Depends on Z
•Happens on length scales of many Angstroms (10-10 m)
•Strong interaction ~ fermi (10-15 m)
p
e
~10 MeV/cm 1 GeV/m 10-10 J
1.6x10-19 J/eV
Measuring Momentum
•We measure the momentum of a charged particle by determining its trajectory in a known magnetic field.
•Simplest case: constant magnetic field and pB trajectory is a circle with p=0.3Br (GeV/c, T, m)
•We measure the trajectory of the charged particle by measuring its coordinates
•(x, y, z or r, z, , or r, , ) at several points in space.•Simplest case: determine radius of circle with 3 points
•We measure coordinates in space using one or more of the following devices:
•Wire Chamber: (~1-2 mm) •Drift Chamber (or TPC): (~50-250um) •Silicon detector: (~5-50 um)
Cherenkov radiation
• Cherenkov radiation occurs with following conditions– There is a medium with index of n(>1), not
vacuum– The particle traverse the medium with a
speed exceeding the speed of light (c/n)• Cherenkov radiation was discovered by
P. A. Cherenkov in 1934– Interpreted by I. M. Frank and I. E. Tamm
using classical electromagnetic dynamics– All of three won Nobel prize of 1958!
• Electromagnetic radiation always occur!– Radiation is occurred whenever dielectrics
recovers from polarized state produced by the electric field of a moving particle.
– However, the radiation will be erased by a coherence with a radiation from different position and phase.
– If the particle speeds more than c/n , the radiation will not be vanished in a certain direction (cos(c)=(n)-1) like a shockwave, and thus Cherenkov photons can come out
Electron (Positrons) and Photons
•At high energies, electrons bremstrahlung and photons pair produce•We’ll use this to measure high energy particles in a “electromagnetic calorimeter”•Use strong interactions to measure in a “hadronic” calorimeter
So What Would You Build?
By the way, who was right?
dN/dy ~ 220-230 per chargedNK+/dy ~ 40dNp/dy ~ 28Net baryon density at mid-y small, but not 0 B small
PHENIX as ultimately built
The “Global” DetectorsBeam-Beam Counters (BBC) Zero-Degree Calorimeters (ZDC)
Forward Calorimeter (FCAL)Multiplicity and Vertex Detector (MVD)
Where is PHENIX BBC?
NorthSouth
144.35 cm
⊿η = 3.1 ~ 4.0
⊿φ = 2π
Hardware Component
BBC has 64 elements for North and South arm.
Each element is assembled byQuartz Cherenkov radiator(th=.7)
and meshed dynode PMT.
ReadoutAnalog signal (PMT output) from BBC
Digitized at Front End Module (FEM)• TDC0 (for ADC gate)• TDC1 (for Local Level1)• ADC
Accumulated in AMU
Data Collection Module (DCM)
Event Builder
PHENIX Raw Data Formatother subsystem data
BBC Local Level 1
Global Level 1 decision
Minimum bias at Run4 (Au+Au)( BBCN>=2 & BBCS>=2
& BBCZ<36 [cm] )&
( ZDCN & ZDCS )
BBLL1Selected(ZDC&BBLL1)
ZDC triggered
Slewing Correction
)log()( ADCcADC
baxf
ADC [ch] ADC [ch]
before correction
after correction
Slewing effect was corrected by this empirical function
(Reference time) – (PMT hit time) of typical PMT
a, b, c : constant
ADC : after pedestal subtraction
Intrinsic time resolution : 40±5ps
details in PHENIX Technical Note 393
BBLL1Selected
(ZDC&BBLL1)
ZDC triggered
Z-Vertex and Time zero
TN/S : average hit time, c : light velocity, L : 144.35 cm
2
/22
cLTT
cTT
NS
NS
• Z-Vertex
• Time zero
BBC North
BBC South LL
Vertex position TNTS
Resolution at RUN2 (Au+Au)
222
222
222
PCZDCPCZDC
ZDCBBCZDCBBC
PCBBCPCBBC
Time Zero : 20 [ps]
Z-Vertex : 0.6 [cm]
( at Run2 )
BBCZ - PCZ BBCZ - ZDCZ PCZ - ZDCZ
What does BBC detect?
• 50% of external track was estimated compared to all injected particles using HIJING Au+Au 130GeV events. inner ring = 43%middle ring = 52% outer ring = 57%• Main background source is beam pipeBeryllium (thickness 1.02 [mm]) : < 75 [cm]Stainless Steal (thickness 1.24 [mm]) : < 200 [cm]
(a) : Internal track coming from collision
(b) : External track not coming from collision
beam pipe
Z-direction
R-d
irec
tion
Collision point (a)
(b)
BBC
• inner ring
• middle ring
• outer ring
RING ID
BBC
Dead PMT in South
Reaction Plane by BBC
-- no correction -- ring-by-ring gain correction-- average subtraction (shift correction)-- fluttening
azimuthal angle Φ
Ψ (BBC North)
Ψ (
BB
C S
ou
th)
Corrected Reaction plane correlation
details in PHENIX Analysis Note 151 : S. Esumi et al.
(Univ. of Tsukuba)
Ignore 4 PMTTo keep hexagonal
symmetry
Background SourceThis is all vertex position of each secondary particles that are injected to BBC. Fig.10 is electron or positron at each vertex position. Fig.11 is charged pion. Almost of electron and positron are produced at beam pipe of Stainless steal.
electron, positron at each position (Fig. 10)
π+, π- at each position (Fig. 11)
Beam Pipe
Stainless steal
BBC
inner edge of central magnet inner edge of central magnet
(Fig. 12)
MVD
Beryllium pipe
BBC
Location, Location, Location
•There is a lot of physics at forward rapidities•In a collider, you need to have a DX magnet to steer bunches so they collide
•Spatial Distribution of Charged Particles shown below•Large Separation = Easy Timing = Very Clean Trigger against Beam Gas and Beam Scrape
Hadronic Interaction:Au-Au --> X 6.8 barns-:AuAu --> AuAu + e+e- 33 kbarnsAuAu --> AuAu + 2(e+e-) 680 barnsAuAu --> AuAu + 3(e+e-) 50 barns-N: L(-N )=1029 cm-2s-1 2<E<300GeVAuAu --> Au+Au* 92 barns X+neutronsAuAu --> Au*+Au* 3.670.26 barns X+neutrons Y+neutrons
Collider Processes•You’re probably familiar with the “Hadronic Interactions”•When colliding large nuclei, the Z creates a large photon flux
•ZDC exploits this for a luminosity measurement•Also interesting physics (UCP program, AN063)
Hadronic Interaction
Peripheral Interaction
ZDC Design
ZDC Calorimeter construction:•Tungsten absorber/ fiber (C)sampling•2 Lint/module, 3 modules total•C sampling filters shower secondaries•Uniform response vs. impact point
e,beam
NIM A 470:488-499,2001, nucl-ex/0008005Fiber response vs. angle
(deg) (deg)
Drift Chamber for PHENIX(basic information)
• Main purpose:– Precise measurement of the
charged particle’s momentum– Gives initial information for the
global tracking in PHENIX
• Acceptance:– 2 arms 90º in each – ±90 cm in Z– 0.7 units of
• Location:– Radial :2.02<R<2.48 m– Angular:
• West: -34º < º
• East : 125º < º
Drift Chamber design
• Multiwire jet-type drift chamber (~12800 readout channels)
• 6x80 (r - ) wire nets per arm
• Titanium alloy support frame with 20 C-shell openings (Keystones)
• Independent signal readout from both sides (North, South) DCH Frame
Wires
Keystone
DCH Operation Principles
• To reconstruct charged particle track DC samples a few points in space along the path of the particle. One such point is called a “HIT”
• Registration of one HIT is based on a few physical processes:– When charged particle transverse the gas volume of the DC it creates clusters of
primary ionization on its way– Electrons of primary ionization drift from the point of ionization to anode wires along
electric field lines– Electrons of primary ionization create avalanches in the vicinity of anode wires – Back drift of posistively charged ions generate measurable signal on anode wires which
is amplified, shaped and discriminated
• To register a HIT in the DC:– Carry out drift time measurements: Start - collision time measured by BBC; Stop - time
when signal appears on the anode wire– Drift time (t) can be tranformed into drift distance (x) if calibration curve is known x = x(t)– Working gas is chosen to have an uniform drift velocity in the active region linear xt
relation can be used x = Vdr · t
Wire net configuration
• 6 radial layers of nets (X1,U1,V1,X2,U2,V2)
• X nets – measure coordinate of the track
– 12 anode wires in each X net
• UV (stereo) nets – measure Z coordinate of the track
– 4 anode wires in each UV net
• Cathode nets separate anode nets (see figure)
• Total of 80 anode nets per arm evenly distributed in
Wire net configuration (II)
• Group of 4 anode-cathode
nets makes a keystone
• Stereo nets starts in one keystone (n) and ends in the neighbouring keystone e.g. (n+1) for U, (n-1) for V
• The tilt of UV nets along allows measurement of Z component of the track
Gas mixture choice
• 50% Ar - 50% C2H6 mixture is chosen for operation based on:– uniform drift velocity at E~1
kV/cm– High Gas Gain – Low diffusion coefficient
• In Year2 ~1.5% Ethanol was added to the mixture to improve HV holding of the nets
Drift field configuration
• Specific field configuration around anode wire called drift region is created by “field forming” wires:
– Cathode Wires – Create uniform drift field between anode and cathode
– Field Wires – Create high electric field strength near the anode wire
– Back Wires –Stop drift from one side of the anode wire
– Gate Wires –Also create high field near the anode wire, Localize the drift region width
Cathode
Back
Gate
Anode
Field
Drift Field Configuration (II)
• Here is what happens when the charged particle passes through the wire cell
• Note that only even wires collect charge due to the back wires that block the odd anode wires !
• Back wires solves left-right ambiguity problem
Tracking principles
Main assumptions:
• Track is straight in the detector region
and variables defined on the figure
•Use hough transform – calculate and for all possible combinations of hits and bin those values into hough array – 2D histogram on and
• Look for local maxima in hough array that surpass the threshold
Track Candidates
• The results of the hough transform are track candidates
• Several stages of hit association and track purging follows
• Finally we left with the following tracks
X1X2 and X-only tracking
• First we look for tracks with X1 and X2 hits
• Remaining unassociated hits goes into X1 only and X2 only tracking
• All the track candidates are being liked after this and Z information is being applied to them by PC1-UV-vertex tracking
Final results
Construction and assembling
• Mechanical design and production – PNPI (Russia)
• Front Electronics – SUNYSB• Wire net production, assembling -
PNPI,SUNYSB
PC1 on DCh
•Five planes: East PC1,3 & WEST PC1,2,3=90°, ||=0.35•80m2 MWPC, pixel cathode readout, •172800k readout channels, •1.2% 0 (PC1) with electronics on back
Performance: cosmics
Gain curvesRunning at 1-2*104
Performance: cosmics
efficiency
Position resolution in Z (cosmics)
chamber
Wire dist
(mm)
Z-resol.
(mm)
Perp res
(mm)
Rad.
Thickn.
PC1 8.4 1.7 2.5 1.2%
PC2 13.6 3.1 3.9 2.4%
PC3 16.0 3.6 4.6 2.4%
measured
Performance Au+Au central
What is RICH? Cerenkov photons from e+ or e- are detected by array of PMTs
mirror
Most hadrons do not emit Cerenkov light
Electrons emit Cerenkov photonsin RICH.
Central Magnet
RICH
PMT arrayPMT array
•Primary electron ID device of PHENIX
•Hadron rejection at 104 level for single track
•Full acceptance for central arms•|y| < 0.35 ; = 90 degrees x 2
•Threshold gas Cherenkov•Using CO2( th ~ 35)•eID pt range : 0.2 ~ 4.9 GeV/c
•PMT array readout•pixel size ~ 1 degree x 1 degree
Why cherenkov radiation is Ring in RICH?
• Pure Optics of the photon!• Suppose that the charged particle
emerge to the radial direction• Mirror is spherical, so..
– Spherical mirror focuses all the photons emitted to a certain angle (c) with refer to the radial direction
– The focus point is at a distance of the half of the diameter of spherical mirror and at a angle of c with refer to the radial direction
• If a particle is not moving on the straight line from vertex point(0,0), the focused ring will be distorted!
112
222
2
22
_ 370,sin
eVcmcmr
zdE
cmr
zLN
eedc
eeelectronphoto
L : path length of particles in radiator
εc : collecting Cherenkov light efficiency
εd : quantum efficiency of photo electron conversion
Gas Vessel
The vessels are designed and fabricated at Florida State University.
• Two RICH detectors– One for each arm– Weight: 7250 kg /
arm– Gas volume: 40 m3 / arm– Radiator length: 0.9 - 1.5 m
• Mirror system – Radius : 403 cm– Surface area: 20 m2 / arm
• Photon detector– 2560 PMTs/arm
• Radiation length– CO2: 0.41%– Windows: 0.2%– Mirror panels: 0.53%– Mirror support: 1.0%– Total: 2.14%
RICH Mirror• Segmented spherical
mirror• Reflection surface
– Aluminum made• Mirror mounts are
adjusted so that all optical targets are within 0.25 mm of the designed spherical surface.– graphite fiber epoxy
• Mirror support structure– graphite fiber, Delrin
Rohacell foam core (1.25 cm thick)
Gel-coat (0.05 mm thick)
4 ply graphite-epoxy (0.7 mm thick)
Structure of the mirrorCompleted mirror array of the first RICH
Design of 3 points mirror mounts
Mirror panels are mounted by adjustable 3 point mounts on the frame bars
Mirror, mirror, mirror…
RICH (mirror alignment)
• After mirrors are installed, the RICH vessel is rotated up in the same orientation as on PHENIX carriage
• Positions of optical targets placed on mirror surface were surveyed with a computerized theodolite system (MANCAT).
BNL survey crew were measuring the optical targets on the mirror during the mirror alignment.
Alignment calibration (Once in RUN)•Accumulate all the hit PMTs around tracks for totally 56 mirrors
•14(mirrors)*2(side)*2(arm)•Adjust mirror positions so that ring centers match projected points of tracks
RICH in Operation! from Year-1 (I)
High PT electron candidate is seen!
Candidate selected with RICH, DC, and EMCal.PHENIX RUN 12280 SEQ 0014 EVENT 850
View from North Side
South Side
East Arm West Arm
RICH EMCal
RICH ring(6 PMT hit)
EMCal hit(2.5GeV)6 PMT RICH ring
2.55 GeV/c track2.5 GeV EMCal hitelectron candidate
EMCal
RICHPC1
DC
EMCal
RICHPC1
DC
TOF
TECPC3
How to identify electrons using RICH
• Starting from track• Calculate projected track point on
PMT according to the mirror alignment– Mirror alignment calibration is very
important!• Define Minimum and Maximum
radius of possible ring by the track– Minimum and Maximum are predicted
based on the simulation study• Check several quantities in the region
of (min)<r<(max)– How many number of PMT hit?– How many cherenkov photons hit?– How is the ring shape?– How is the timing of signal?
• If above checked quantities fulfilled conditions, tag it as electron!– ex. Number of PMT hits >=3– ex. Number of photo-electrons>9
Electrons in Ratio of Energy and Momentum
• Ratio of energy (E) and momentum (p) of associated track
• p and E are measured with DC and EMCal, respectively
• Condition required– PMT hits of more than
two in the ring of 3.4cm<r<8.4cm
– Good ring shape
• Peak is seen at E/p=1, which corresponds to electrons
• There is NO electron peak until Cherenkov hit is requiredGreen: Raw spectra Black: Cherenkov hit required
Blue: Estimated background Red: Background subtracted
0.3GeV<p<0.4GeV 0.6GeV<p<0.7GeV
0.8GeV<p<0.9GeV 1.1GeV<p<1.2GeV
Integration of RICH
• Gas vessel • Mirror• PMT and arrays• Electronics
Purpose of this sectionBe familiar with RICH components
Particle (n)
How do we use gas?
• When a particle travels in gas volume, – If particle speed exceeding the speed of light in gas (c/n)– Photons are radiated – Cherenkov lights!
GAS (radiator) If momentum is known,
we can IDENTIFY particle using Cherenkov light measurements.
Index:n
c
Threshold of light emissionn
Emission anglecosc =(n)-1
Light YieldProportional to L and sin2c
L
PMT and arrays
• Photon detection device– Hamamatsu H3171S
• Cathode Diameter: 25 mm• Tube Diameter: 29 mm• Cathode: Bialkali• Gain: > 107
• Operation Voltage: -1400 ~ -1800V• Rise Time: < 2.5ns• Transit Time Spread: < 750ps
• A Winstone cone – shaped conical mirror is attached to each
PMT – Entrance: 50 mm, Cut off: 30
• Supermodule (2x16 PMTs grouped)– 40 super-modules per one side– 4 sides * 40 * 2* 16 = 5120 PMTs
• 8 PMTs share the same HV channel pixel size 1 degree x 1 degree
The arrays are fabricated at SUNY
Summary of hardware
• Electron go thorough the RICH gas volume,– Cherenkov photons emitted– Photons are reflected by
mirror and focused on the PMT surface
– PMT detect photons
Cerenkovphotons from e+ or e- are detected by array of PMTs
mirror
Most hadrons do not emit Cerenkov light
Electrons emit Cerenkovphotonsin RICH.
Central Magnet
RICH
PMT arrayPMT array
Cerenkovphotons from e+ or e- are detected by array of PMTs
mirror
Most hadrons do not emit Cerenkov light
Electrons emit Cerenkovphotonsin RICH.
Central Magnet
RICH
PMT arrayPMT array
Identify electron from 0.02 to 4.9 GeV/c.
What can we do with RICH?
• Measure several kinds of proposed QGP signals. – Deconfinement
• J/ toe+e-– Chiral Symmetry Restoration
• Mass, width, branching ratio of to e+e-, K+K- with M < 5 MeV
– Thermal Radiation of Hot Gas• Prompt * to e+e-
– Strangeness and Charm Production• Production of , J/, D mesons• Single electron
Electron ID is essential for above measurements.
Low mass e+e- pair
• Chiral Symmetry Restoration– Mass, width of to e+e-
• Thermal Radiation of Hot Gas– Prompt * to e+e-
We did not yet get significant results in AuAu.NEED more statistics
]2 invriant mass [GeV/c-e+e0.6 0.7 0.8 0.9 1 1.1 1.20
20
40
60
80
100
120
140
160
180
200
220
Unlike-sign Pair mass HmassERT2Entries 9612Mean 0.6634RMS 0.5068
Could be
Recently, we have an indication of peaks in dAu data.
Y. Tsuchimoto
How to identify electrons?
• Main parameters in RICH– Distance between ring center and track
projection (disp)– Number of hit PMT in a region (n0)– Number of photo-electron in a region
(npe0)– Ring shape (chi2/npe0)
1. According to the track information, projection point is calculated.
2. Find PMT hits near projection point in the region (3.4 cm < r < 8.4 cm)Numbers come from position resolution of PMT
hits.
3. Above parameters are calculated using projection point and PMT hit information
How good it is.
• Energy / momentum– For electron, it should be 1.
• RICH cut suppress back ground by about factor 100.
Energy / Momentum
All Charged particle
Apply RICH cut
BGRICH works well.We can continue making progress in QGP physics using electron measurements
Extension of Charged Hadron PID Capability
Aerogel together with TOF can extend the PID capability < 10 GeV/c• Without TOF, no K-proton separation at pT < 5 GeV/c.
PHENIX-MRPC: Detail
• 6 gaps (230 micron).• Gas mixture: R134A (95%), Isobutane (5%) at 60 cc/min.• HV: 7.5 kV
Gas gap = 0.23 mm
Readout strip thickness = 0.5 mm
Total active area width = 11.2 cmHoneycomb width = 12 cm
Glass
Electrode
MylarPC boardReadout pad
HoneycombStandoff
Inner glass width = 11.2 cm
Outer glass width = 11.5 cm
PCB width = 13 cm
Outer glass = 1.1 mm
Inner glass = 0.55 mm
carbon tape = 0.9 mm Mylar thickness = 0.25 mm
PCB thickness = 1.5 mm
Honeycomb thickness = 9.5 mm
Strip width = 2.81 cmStrip interval = 0.3 cm
TOFW (Final Configuration & Position)
• Coverage Area of 4 m2
• 128 Chambers• 1024 Readout
Channels• Two Sectors
PID Upgrade Completed Track Correlation Methods
How does it (TOF) look like ?
- 960 plastic scintillators with 1920 PMT’s - locates at 5 meter from the vertex- Rapidity (-0.35~0.35), 45 degree in phi, ~1/3Sr
Phenix (East-Arm)
“panel” “slat”
“E1 sector”
“E0 sector”
Basics of measurements
222
222
12
22
1
12
22
10
tv
ttvx
tttt
lightlight
light
light
vtt
x
vltt
t
2
221
0
210 100ps
then 1.6cm
Precise TOF and Hit position
Double hit - Lose timing information must occupancy level low - Consistency between ratio of ADC and TDC diff. light
aa
vtt
x
lx
2
log2
21
2
1
What does it give now ? (First of all, ) Hadron
Identification
- Pion, Kaon, proton, and deuteron are clearly identified. - Overall, ~120ps (overall, in m2) time resolution is achieved
(anti-)deuteron
Kaon up to 2 GeV/c, Proton/pion(0) up to 4 GeV/c.Proton/pion(0) changes from “< 1.” to “>1” at ~ 2GeV/c.
What does it give now ? (e.g.#2) Particle Ratio
Before the summary, an idea of Phenix PID upgrade.
Continuous measurement from ~0.5 GeV/c up to ~ several GeV/cfor pi/K/p identification !
Principle of Timing measurement
v
xT 0 v
xLT
0
L
L – xx
PMT1 PMT2
(T0,x0)T1 T2
2
/)( 21 vLTT
vTT
221
TOF
Y position
Cartoon
T1, T2 : Timing measured by PMT1,2L : slat lengthv : light velocity in scintillator
Hadron identification
• Pion, Kaon, Proton and deuteron are clearly identified !– Overall ~ 120 ps (overall, in mass2) time resolution is achieved.
Concept
PID in high pT region• Cherenkov Radiation
Cherenkov Radiator
• Low refractive index• Best index with RICH(CO2) is n ~ 1.01.
Requirements- Refractive index : n~1.01 – Momentum threshold- Light yield : >10 p.e. – Resolving power- Uniformity of the light yield : Needed. – Easy handling - Occupancy in Au+Au collisions : <10% – S/N
Installation Purpose
To enhance the PID capability of PHENIX !!
TOF
Aerogel (+ TOF or RICH)
RICH
Momentum[GeV/c]
K
p
1 2 3 4 5 6 7
0.5 2.5
~10
4.2
Aerogel : (n=1.011.)TOF : 100 ps time resolutionRICH : CO2, (n = 1.00041)
5.53.7
What is Aerogel Counter ?? ( I ) Outline
Cherenkov Counter (non-ring-imaging type)• Cherenkov radiator is Silica Aerogel. (MATSUSHITA, SP-12M)
• Photon is detected by 2 PMTs. (HAMAMATSU, R6233)
• All inner surface is covered with DRP Reflector. (Goretex)
• Integration cube for uniformity of light yield. (Air)
PMT (3inch)
PMT (3inch)
Aerogel (index~1.011
)
Integration Cube (Air)
Reflector (Goretex)
( 11x22x20 cm3
)
What is Aerogel Counter ?? ( III ) Where
RED: AerogelYELLOW: Integration sphereGREEN: PMT
vertex
particle track
z (beam
) dire
ction
azimuthal angle
160 segments
- 4.5m from vertex
- 4.0m along z direction
- 15 deg. in phi
Half of them in Run4
Mechanical Design ( I ) Silica Aerogel
Many many Aerogel tiles!! Y.Miake
Characteristic• Refractive index ~ 1.0114 +/- 0.0008
• Density ~ 40 mg/cm3
• Hydrophobic
• Long term stability ( KEK-Belle )
• Transparent for 10mm thickness - 64% @ 400nm, 88% @ 550nm
• Very fragile
- Silica aerogel with lowest refractive index commercially available !!
He is godfather of aerogel !!
Where is the EMCal?
PbSc
PbGl
East
West(arm=0)
East(arm=1)
0
1
2
3
0
1
2
3
Principles of Detection:
• Electrons and Photons interact electromagnetically (bremsstrahlung and pair production)
electromagnetic shower• Strongly interacting particles: hadronic shower, MIP
• Calorimeter measures energy, position, and TOF
• PbSc – sampling calorimeter, layers of lead and scintillator
• PbGl – homogeneous calorimeter, lead-glass Cherenkov radiator
• Light read by PMT
• Charged shower particles generate Cherenkov photons in the PbGl
• The Ch. Photons propagate with a wavelength dependent
attenuation to the PMT • Shower depth:
• Number of generated Cherenkov photons:
Principles: PbGl
tE
Eln
X
X
c
max 0
0ENCherenkov
Non-Linearity Effects
Absorption
Leakage
photons
electrons
Non-linearity effects have to be corrected
Principles: PbSc
Pb + Scintillator
generateshower
generatelight
•Absorber : Pb•Scintillator: 1.5 % PTP / 0.01 % POPOP
Light collection
Non-Linearity in the PbSc
finite light attenuation length in WS fiber
energy leakage
0
0
E
EEmeas
Two parts make one detector!
• PbSc: – Excels in timing– Better linearity in response– In principle, response to hadrons better understood
• PbGl: – Excels in energy measurement– Better granularity– Proven system (WA98)
• Two detectors = different systematics increase confidence level of physics results
The Leadglass Detector
PbGl-Sector
• 2 Sectors PbGl
• 1 PbGl Sector• 16x12 supermodules (SM)
• 1 PbGl SM• 6x4 towers • Separate reference system
• 1 FEM • Reads out 2x3 supermodules or 12x12 towers
• TF1 PbGlass • 51% Pb-Oxide • Wrapped with aluminized mylar foil•New developed HV-bases
PbGl Structure - Module
1 PbGl tower = 1 PbGl module
PbGl Structure II
PbGl Structure III
The Lead Scintillator
PbSc Structure• 1 Sector = 6x3 Supermodules (SM)• 1 PbSc SM = 12x12 towers • PbSc towers: 5.52 x 5.52 x 33 cm3 (18 X0)• 15552 blocks total
1 PbSc tower: • 66 sampling cells• 1.5 mm Pb, 4 mm Sc• Ganged together by penetrating wavelength shifting fibers for light collection• Readout: FEU115M phototubes
1 FEM reads out 1 Supermodule
PbSc Supermodule
Hadron ID with TOF
• Measure space points
• Deduce o Vertex locationo Good momentum resolutiono Decay lengthso Distance of Closest Approach (DCA)
What is measured?What is measured?
Introduction to Semiconductor Introduction to Semiconductor DetectorsDetectors
L
Primary vertex
Secondary vertex
Example:
L = (p/m) c
• By measuring the decay length L, and the momentum, p, the lifetime of the particle can be determined
• Need accuracy on both production and decay point
Also, by measuring the decay length, L, and knowing the lifetime of the particle, the momentum can be determined
• Decay lengths
What is measured?What is measured?
0sKJ/ΨB
Introduction to Semiconductor Introduction to Semiconductor DetectorDetector
D± = 312 m, D0 = 123 m B± = 501 m, B0 = 460 m
• Distance of Closest Approach (DCA)
b = distance of closest approach of a reconstructed track to the true interaction point
What is measured?What is measured?
beam
Beam b
Introduction to Semiconductor Introduction to Semiconductor DetectorDetector
DCA distribution for single simulated pions in 3<pT<4 GeV/c. Simulation is done with 200 micron pixel layers and 650 micron strip layer. The passive material is 1.0% per pixel layer and 2.75% per strip layer.
Expected DCA Expected DCA resolution of VTXresolution of VTX
Au+Auat 200 GeV
~ 40 m
Primary vertex Secondary
vertex
• Semiconductor with moderate bandgap (1.12 eV)
• Thermal energy = 1/40 evo Little cooling required
• Energy to create e/h pair (signal quanta) = 3.6 eV3.6 eV c.f Argon gas = 15 eV15 eVo High carrier yield o Better energy resolution and high signal
no gain stage required
Why silicon?Why silicon?
Introduction to Semiconductor Introduction to Semiconductor DetectorDetector
• High density and atomic number o Higher specific energy losso Thinner detectors o Reduced range of secondary particles
Better spatial resolution
• High carrier mobility Fast!o Less than 30 ns to collect entire signal
• Industrial fabrication technique available• Advanced simulation packages
o Processing developmentso Optimization of geometry o Limiting high voltage breakdown o Understanding radiation damage
Why silicon?Why silicon?
Introduction to Semiconductor Introduction to Semiconductor DetectorDetector
• Cost of Area coveredo Detector material could be cheap – Standard
Sio Most cost in readout channels
• Material budget o Radiation length can be significant
Tracking due to multiple scattering
• Radiation damageo Replace often or design very well
Disadvantages?Disadvantages?
Introduction to Semiconductor Introduction to Semiconductor DetectorDetector
P-N JunctionP-N Junction
One of the crucial keys to solid state electronics is the nature of the P-N junction. When p-type and n-type materials are placed in contact with each other, the junction behaves very differently than either type of material alone. Specifically, current will flow readily in one direction (forward bias), creating the basic diode.
Near the junction, electrons diffuse across to combine with holes, creating a "depletion region".
Introduction to Semiconductor Introduction to Semiconductor DetectorDetector
• Charge particles– Bethe-Bloch
• Not covered o Neutronso Gamma Rays
Compton scattering, pair production, etc…
Energy depositionEnergy deposition
Introduction to Semiconductor Introduction to Semiconductor DetectorDetector
Status of the VTX Project in PHENIXStatus of the VTX Project in PHENIX
Central Silicon Vertex Trackers
“VTX”
Pixel
Strippixel
VTX Layer R1 R2 R3 R4
Geometrical dimensions
R (cm) 2.5 5 10 14
z (cm) 21.8 21.8 31.8 38.2
Area (cm2) 280 560 1960 3400
Channel count Sensor sizeR z (cm2)
1.28 1.36(256 × 32 pixels)
3.43 × 6.36(384 × 2 strips)
Channel size 50 425 m2 80 m 3 cm(effective 80 1000 m2)
Sensors/ladder 4 4 5 6
Ladders 10 20 18 26
Sensors 160 320 90 156
Readout chips 160 320 1080 1872
Readout channels 1,310,720 2,621,440 138,240 239,616
Radiation length(X/X0)
Sensor 0.22% 0.67 %
Readout 0.16% 0.64 %
Bus 0.28%
Ladder & cooling 0.78% 0.78 %
Total 1.44% 2.1 %
Pixel detectorPixel detector Strip detectorStrip detectorBarrel VTX ParametersBarrel VTX Parameters
BEAM
Strip
Pixel
Layer radius Detector Occupancy in Central Au+Au collision
Layer 1 2.5 cm Pixel 0.53 %
Layer 2 5.0 cm Pixel 0.16%
Layer 3 10.0 cm
Strip 4.5 % (x-strip) 4.7 % (u-strip)
Layer 4 14.0 cm
Strip 2.5 % (x-strip) 2.7 % (u-strip)
Precursors to PHENIX / 12 - the verdict in the 2nd round
(Not too much time spent on mincing the words…)
Reject all three because of major deficiencies
Emphasis should be on QGP photons and electrons (implicit: STAR already does hadrons)
Get together (lead by Sam Aronson), and design one single detector
Maximum cost $30M