Upgrade of PID for BESIII

June 13, 2006Institute of High Energy Physics, Beijing, China

Yuekun Heng (hengyk@mail.ihep.ac.cn)

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Outline

Present TOF design Physics requirements for PID Upgrade to MRPC?? Upgrade to Internally reflecting Ch

erenkov detector:CCT, TOP, Focusing DIRC

Summary and discussion

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1. Present TOF Design

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Present barrel TOFThe option of barrel TOF is determined after many

discussions in June, 2005. Two layers of scintillator will be used for barrel.

Barrel TOF

Endcap TOF

CsI Calorimeter

Drift Chambe

r

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Fig. Assembly of barrel TOF.

Barrel TOF alignment

Fig. BTOF side view. To save space, the base of PMT housing is 6-sides-shaped and the inner and outer layer is across. It has four screws to connect the scin.

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Endcap TOF structure

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Item Barrel time reso.

Endcap time reso.

Intrinsic time reso. of one TOF layer for 1 GeV muon

80~90 ps 80 ps

Uncertainty from electronics 25 ps 25 ps

Uncertainty from bunch length 15 mm ， 35 ps

15 mm ， 35 ps

Uncertainty from bunch time ~20 ps ~20 ps

Uncertainty from Z position 5 mm,25 ps 10 mm,50 ps

Resolution of expected time of flight 30 ps 30 ps

Total time reso, one layer of TOF for 1 GeV muon

100~110 ps 110~120 ps

Total time reso, double layer of TOF for 1 GeV muon

90 ps

Analysis of Time reso.

Non T

OF

~60ps

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Why two layers? Time reso. For Kaon and p

ion is worse 20% than muon in experiences.

Time reso. Of two layers totally is from 100ps to 110ps for kaon and pion.

That time reso. Can separate kaon/pion of 0.9GeV in the middle of barrel.

Contriburion Time reso. For 1GeV Muon

Time reso. For Kaon/pion

Non TOF 60ps

One layer of scin. Intrinsic

80-90ps

One layer ofScin. Totally

100-110ps 110ps-130ps

Two layers,Totally

80-90ps 100ps-110ps

Capability of separation

of Kaon and Pion

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2. Physics targets for PIDand our space limits

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K/πmomentum on BESIII BEPCII: 2.0~4.2GeV BESIII:

Charm physics:J/Psi, Psi’, Psi’’

Tau Physics K/π momentum: almos

t all<1.5GeV K/π seperation: 1.2GeV

is enough Present TOF: 0.9GeV(2si

gma,95%)

Next target

Momentum distribution for hadrons at J/psi

BESIIIExperimental Searching forD0D0 Mixing (From He Kanglin ) Big challenge to PID (Kπchannel)

Main backgrounds come from the double miss-PID

Searching in semi-leptonic decay modes are experimental difficulty with 2 missing neutrino (hard to reduce background contribution to 10-4)

Monte Carlo study with different PID (TOF resolution)

BESIIIDetection efficiency vs TOF resolution

Efficiency vs time resolution

30

32

34

36

38

40

60 65 70 75 80 85 90 95 100 105 110 120 130

Time resolution(ps)

effi

cien

cy(%

)

BESIIIBackground rates vsTOF resolution

Background vs time resolution

0

1

2

3

4

5

60 65 70 75 80 85 90 95 100 105 110 120 130

Time resolution(ps)

Bac

kgro

und(

10-4

)

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PID space limitsBanded to MDC

outer barrel of Carbon-fiber

R-direction space: 81cm-92.5cm

Scintillator Length: 2320mm

Coverage:~82%

PID space

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3. Upgrade to MRPC??

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Target analysis for MRPC To get 1.2GeV separation of K/pi, totally time reso. <8

0ps Non-TOF is 60ps, TOF <60ps,

Plastic scin. Can’t give so good time.MRPC may be OK.

To cover dead area of MRPC, overlap of two layers of MRPC is needed.

To reduced electronics, MRPC should be long strip and readout by two ends.

Long-strip MRPC needs much more studies.

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MRPC results 试验 尺寸 cm 时间分辨

VEPPW e+e-

小尺寸0.1mm 缝隙 75ps （流光模式）

NA494X30

0.1mm 缝隙） 50ps （流光模式）

HARP 200X15X1 140-180ps

FOPI Upgrade

9.1X180(long strip)

70-80ps （束流试验）

STAR 24X22X9 60ps （束流试验）ALICE 120X13X2.5 38ps

Timing RPC R&D

160X10X20(long strip)

50-75ps束流试验

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III.

4 gaps, 0.3mm/gap

HV:10kV/mm

Preamp: not say

GAS: 85% C2H2F4 5% iso- C4H10

10%SF6 ，达到的时间分辨为 75ps

BESIIIMRPC optionbakelite as the resis. plateStructure:•Resi. Plate: bakelite•gaps: 6;•Chamber: 8cm(W)X190cm(L)•gas ： 90%Freon, 5%iso-butane, 5%SF6•Preamp ： Star

Signal pulse•HV: 16kV/1.2mm)•Readoud pad:3X6cm•Rise time:~2ns•Time Reso.:70 ～ 110ps

The results for a MRPC sample where the fish-line is rolled in longitude direction

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Our tests

钓鱼线竖绕板室

BESIII钓鱼线竖绕板室的初步实验结果（吴金杰）

Structure:•Resi. Plate: bakelite•gaps: 6;•Chamber: 8cm(W)X190cm(L)•gas ： 90%Freon, 5%iso-butane, 5%SF6•Preamp ： Star Signal pulse

•HV: 16kV/1.2mm)•Readoud pad:3X6cm•Rise time:~2ns•Time Reso.:~110ps

Reasons: gap not well

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钓鱼线横绕的 MRPC 实验结果（安正华）

两边气槽和边框共占去 3cm ，有效面积约 65 ％。

MRPC signal

BESIIIT-Q correction

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14.5kV MRPC: Time reso.

上图是 MRPC 幅度谱在 100 － 400 的时间分辨由此可计算出 MRPC 的本征时间分辨sqrt(3.907*3.907-2.837*2.837)*25ps=67.16ps

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14.5kV MRPC 实验总结 时间分辨

上图是 MRPC 幅度谱在 401 － 2047 的时间分辨由此可计算出 MRPC 的本征时间分辨sqrt(6.709*6.709-2.926*2.926)*25ps=150.93ps

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4. Internally reflecting Cherenkov detector:CCT, TOP, Focusing DIRC

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Cherenkov detectorsName Principle Range of

PIDreadout

美国 SLACBabar－ DIRC[2]

Quartz + long bar +Water tank + PMT

～ 4GeV 11000 PMT，

日本 KEKBELLE － ACC[3]

ACC, Threshold type ～ 3.5GeV 2000 Fine-Mesh PMT

美国CLEO-III RICH[4]

LiF as the radiator,TEA gas to convert photon-electron, MWPC to detect the ring of cherenkov

～ 2.8GeV 230,000 channels electronics

CERNLHC-b RICH[5]

Two RICHs. RICH1: 5cm thick ACC and 95cm thick C4F10 as radiator;RICH2: 180cm thick CF4 as radiator

～ 150GeV Hybrid PhotoDiode, Much space

CERN LEPDELPHI RICH[6]

Gas of C5F12 and liguit of C6F14,

as radiator, ~25GeV gas photodetector

+ MWPC to readout

BESIIIInternally reflecting cherenkov detector

Using internally reflecting cherenkov light

Parameters to know: track direction Cherenkov light(x,y), or

(theta, phi) Transmitting time:

BESIII3 options (refers to Honscheid ,Ohshima,Vavra,)

CCT(Cherenkov Correlated Timing )

• 1D Timing only

a) Time is related to cherenkov angle

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CCT

Its principle is to measure the time of the cerenkov light to separate particles.

We did simulations. There are about 10 PEs for 2inches PMT with QE of 20%. reso.

Transit time spread of PMT: Line-focus type PMT, 250ps (xp2020) Fine-mesh type PMT, 180ps (R5924) Micro-Channel-Plate type PMT, 50ps

(R2809U)

BESIIIPotential of CCT: MCP-PMT to give good time reso.

Refer to:Jochen Schwiening, SLAC

T. Ohshima, Nagoya Univ.

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Comparison of K/ sep. TOF+TOF TOF+CCT

Fig. K / separation for Double TOF Fig. K / separation for TOF+CCT

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TOP: Time of Propagation Principle: only Φcandθc can determine cherenkov angle. TOP and Φ can deduce them.

Quartz bar’s sides are vertical and conse

rve the Φc. Quartz lightguide is needed to

ensure the light direction out of quartz bar

Fucussing Mirror: fucussing the parrel light because of the thickness of quartz bar.

Photon detector is placed opposite of mirror.

To deduce dead area, the detection end will be placed in opposite ends for adjacent counters

BESIIIUncertainties of TOP

Chromatic error. 5‰ 。 Uncertainty of Φc. Mirror’s res

olution and PMT position resolution, can be 9mrad.

Time spread of PMT Start time resolution Thickness of quartz bar. High sp

eed particle transmit quartz bar (20mm) needs about 66ps. But when particle inclined transmits, the uncertainty will be reduced because particle transit time and light transit time lessen it.

Position of injected particle. ~2mm ， ~10ps

Photon electron number

Cherenkov ring by Y.Enari Using TOP. Particle 4GeVπ ， position:1m.

2GeVπ ， position:0.02m 和 1m 处 . TOP resolution VS Φ.By Ohshima.

BESIIITOP: Candidate of Super Belle

Refer to Peter Krizan, Super B factory workshop, Frascati, 2006

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TOP: For BESIII, 1.2 GeV is enough, 1.5 GeV is very good.

Refer to Noriaki Sato, 2005, hawaii

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Focusing DIRC Measure the time and

2dimension position It uses APD or MCP P

MT to measure the time and position of Cerenkov light from Quartz.

No big imaging circles and so no much space is needed.

The money is saved because of smaller quantity of PMT.

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Candidate of Babar’s next plan

From Vavra, Hawaii workshop

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5. Summary 1.2GeV K/Pi separation is needed for BESIII

physics. Now it is only 0.9GeV. Upgrade is nessesary.

<60ps of Long-strip MRPC is OK to give 1.2GeV separation. Experiments is under way. 60ps is not easy.

CCT has good potential for the upgrade. It is simple with MCP-PMT of good time reso.

TOP can give over 1.5GeV separation of K/pi.

Focusing DIRC needs more space, impossible for BESIII

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The End

Thanks a lot!

BESIIIK/Pi difference of cherekov light