High pt project


	Yasuo Miake Univ. of Tsukuba

Future Extention of PHENIX


Basic strategy of PHENIX
	PHENIX as photon, hadron, electron and muon spectrometer
	Rare event detection capability.
		It is natural to extend the PID towards higher pt region.
Strong motivation given;
	Never seen at SPS
	Interesting behaviour at high pt
	Jet Qunching!?

Jet quenching


	Parton energy loss in dense matter
		Analogous to EM energy loss of charged particles in matter
		Dominated by gluon radiation in QCD
	Hard processes/probes are from the earliest stage of the collision
		Could be a good probe of QGP formation

Jet Quench via pt distribution


	One straight way to see the effect
		Extend the pt range helps!
		May be difficult when the other effect involved

Jet Quench via Flavor Dependence


Gluons in QCD stronger interaction than quarks
	Gluon density in nucleon larger in small x
	s_gg > s_qq
	Larger energy loss of gluons than that of quarks
		dEq/dx ~ 1 GeV/fm
		dEg/dx ~ 2 GeV/fm
At high pt, some particles are fragmented more from gluon than quark jet.
	Gluon jets fragment into same number of particles and anti-particles.
	Gluon jets produce more particles ; softer distr.
		Effect of jet qunching can be seen in particle ratios.

　p^-/ p⁺ ratios


Low pt, same numbers of pions produced from gluons and quarks, while at high pt, only (u,d) quark jet contributes.
	pp;
		Saturates at 0.5 (n_d/n_u of p)
	Au+Au;
		Saturates at 1.14 (n_d/n_u of Au nuclei)
Change due to the parton energy loss is small in pions because of smaller contributions from gluons.

　Antiproton/proton ratios


	(u,d) quark jets likely produce a leading proton than antiproton.
		Ratio decreases with pt.
	Gluon jets produce the same number of proton and antiproton with softer distribution.
		At high pt, most of antiproton from gluons, while proton from both valence quark and gluon fragmentation.
		If gluon jets lose more energy, then ratio behavior modified.

Jet quench effect in v₂


	Azimuthal asymmetry provides sensitive measure of initial density distribution.
	More sensitive than pt spectra!?

Charm


	Deacy from D⁰ (open charm) contributes a lot to high pt kaons.
	May enhance the capability of open charm measurement.
	Need further study!

PID capability of PHENIX


	Time-of Flight
		TOF
		PbSc
		BBC
	Cherenkov
		RICH
	EM calorimeter
		PBGl
		PbSc

PID by TOF


	Overall timing resolution <100 ps achieved.
		Pion/Kaon < 2.5 GeV/c
		Kaon/Proton < 4.0 GeV/c

PID by RICH


RICH
	CH4;1.00044
	CO2;1.00041
		g_th= 34
		Pion ; 4.7 GeV/c
		eID; 0.2 - 4 GeV/c
	10 - 15 p.e. achieved!

Additional Cherenkov


RICH
	CH4;1.00044
	CO2;1.00041
		g_th= 34
		Pion ; 4.7 GeV/c
Aerogel
	Best match at 1.005
	Commercially available for 1.007 - 1.07
Samples for test
	1.007
	1.01
	1.015

Extended PID

Aerogel Cherenkov at KEK-B BELLE


	Non-imaging Cherenkov
	960 modules at Barrel, 228 at Endcap.
	Index n = 1.01 - 1.03
	12 x 12 x 12 cm3
	2 Fine-mesh PMT (1.5T)
		R6683(3”) for n = 1.01
		R6682(2.5”) for n = 1.015
		R6681(2”) for n = 1.02
	~ 10 - 20 p.e.

Segmentation of Aerogel


	TOF
		~ 100 cm2 at 5 m
		Sensitive to all > 150 MeV/c
		Backgrounds (low energy e/g’s　 from yoke & EM cal)
		Occupancy 10% in Au+Au
	Aerogel of n = 1.01
		Sensitive to all g > 7.1
		Delta rays in Aerogel (~%)
		Muon from decayed pion
		Backgrounds
	GEANT required!
		Satoshi Takagi assigned

Cost Guestimate


	Coverage of 4 TOF panel equivalent, which is minimum addition.
		150 modules
		300 PMT’s ; 12,000,000 yen
		400 liter; 20,000,000 yen
		Total ; ~40,000,000 yen
	Construction of TOF panels needed if we install on the West.
		TOF 1 panel ; 13,000,000 yen
		Remove lower 2 panels from the East + 1 spare + 1 built

PMT selection


PMT Requirements
	Photon counting
		Gain; > 10**6
		Low dark current
	Non-UV
	Larger diameter
	Cost
Hamamatsu recommended
	2”　 ;　 R6231
	3”　 ;　 R6233

Pulse height distr.of single p.e.’s


	2” R6231
	Clean single photoelectron peak seen.
	Gain of 2x10**6 will be obtained.
		Done by Hamamatsu
		Will be tested at Tsukuba

Index of Aerogel


	Commercially available
	~50k yen / litter
	For the test experiments, n=1.006 -7, 1.015, 1.020 are ordered for 10 liter each.
	Delivered by the end of Aug.

Measurement of Refractive Index


	n = 1.01 successfully obtained.

Simulation for the design


	MonteCalro Simulation
		Cherenkov emission
		Transmission
		Absorption
		Scattering
	Parameterize measured transmission curve
		Λabs
		Λscat

Last points before PMT hits


	Results depends strongly on Λabs and Λscat!

Absorption and Scattering length


	Transport length (L) is assumed to be from Scattering length(L_scat) and absorption length (L_abs)
	Determined from transmittance curve assuming;

Measured Transmittance


Tested with the sample in hand
	Better transmittance observed
	Could depend on LOT and the index
		Need tests with the real sample

Other way to evaluate Λscat


	Measure scattered photons off the Aerogel
	Could be better way to evaluate Λabs and Λscat

Scattered Photons (Exp)


	Very preliminary (1 day old)
	Consistent with scattering length of a few cm at 410 nm
	80 p.e. out of 250 p.e.?
	No directionarity of light expected!?

Scattered Photons (MC)


	Very preliminary (<1 day old)
	KEK parametrizations used
		Λscat ; 3 cm @ 415 nm
		Λabs ; 12 cm @ 415 nm
		Note that transmittance of our sample is different.
	Qualitative agreement

Plan


Kick start the GEANT activity.
	Satoshi Takagi
Evaluate Λabs and Λscat
	Transmission
	Scattering lights
		MC vs Exp
Evaluation of PMT’s
	3” vs 2”
	Position dep. of photo cathode
	Pulse height dist. of 1 p.e.
	Bleeder evaluation
		From 2-2-1-1-1 to 1-1-1-1-1
Design of prototype

KEK test beam plan


	KEK test beam in Dec.
		Proposal will be submitted in September
		Need names of participants
	Prototypes to be built
		Type-A; 12 x 12 w 3”　 (BELLE)
		Type-B; 20 x 20　 w 3”
		Type-C; 20 x 20 w mirror
	Items to be tested
		# of p.e. vs. mom.;　 0.4 - 4 GeV/c
		# of p.e. vs. thickness
		Position of PMT
		Air between Aerogel and PMT
		Direction of stack
	Call for issues/ideas!