Steven Blusk for the BTeV Collaboration

1
Design of the BTeV RICH and its Expected
Performance
Steven Bluskforthe BTeV Collaboration
2
The BTeV Collaboration

• Belarussian State- D .Drobychev,
• A. Lobko, A. Lopatrik, R. Zouversky
• UC Davis - J. Link, P. Yager
• Univ. of Colorado at Boulder
• J. Cumalat
• Fermi National Lab
• J. Appel, E. Barsotti, CN Brown,
• J. Butler, H. Cheung, G. Chiodini,
• D. Christian, S. Cihangir, I. Gaines,
• P. Garbincius, L. Garren,
• E. Gottschalk, A. Hahn, G. Jackson,
• P. Kasper, P. Kasper, R. Kutschke,
• SW Kwan, P. Lebrun, P. McBride,
• L. Stutte, M. Votava, M. Wang,
• J. Yarba
• Univ. of Florida at Gainesville
• P. Avery
• University of Houston
• K. Lau, B. W. Mayes, J. Pyrlik,

Southern Methodist University - T. Coan SUNY
Albany - M. Alam Syracuse University M. Artuso,
C. Boulahouache, O. Dorjkhaidav K. Khroustalev,
R.Mountain, R. Nandakumar, T. Skwarnicki,
S. Stone, JC Wang, H. Zhao Univ. of Tennessee
K. Cho, T. Handler, R. Mitchell
Tufts Univ. A. Napier Vanderbilt
University W. Johns, P. Sheldon, K. Stenson, E.
Vaandering, M. Webster
Wayne State University G. Bonvicini, D. Cinabro
University of Wisconsin M. Sheaff Yale
University J. Slaughter
York University S. Menary
Indiana University RW Gardner, DR Rust Univ.
of Insubria in Como- P. Ratcliffe, M. Rovere INFN
- Frascati- M. Bertani, L. Benussi, S. Bianco, M.
Caponero, F. Fabri, F. Felli, M. Giardoni, A. La
Monaca, E. Pace, M. Pallota, A. Paolozzi, A.
Scicutelli INFN - Milano G. Alimonti, M.
Citterio, P. DAngelo, S. Magni, D. Menasce, L.
Moroni, D. Pedrini, M. Pirola, S. Sala, L.
Uplegger INFN - Pavia - G. Boca, G. Cossail, E.
Degliantoni, PF Manfredi, M. Manghisoni, M.
Marengo, L. Ratti, V. Re, V. Speziali, G.
Traversi INFN - Torino N. Cartiglia, R.
Cester, F. Marchetto, R. Mussa, N. Pastrone IHEP
Protvino, Russia A. Derevschikov, Y.
Goncharenko, V. Khodyrev, A. Meschanin,
L. Nogach, K. Shestermanov, L. Soloviev, A.
Vasiliev University of Iowa C.
Newsom, R. Braunger University of Minnesota
V. V. Frolov, Y. Kubota, R. Poling, A.
Smith Nanjing Univ. (China) T. Y. Chen, D.
Gao, S. Du, M. Qi, BP. Zhang, JW Zhao
Ohio State University
K. Honscheid, H. Kagan Univ. of Pennsylvania
W. Selove Univ. of
Puerto Rico A. Lopez, W. Xiong
Univ. of Science Tech. of China - G. Datao, L.
Hao, Ge Jin, L. Tiankuan, T. Yang, XQ
Yu Shandong Univ. (China) CF Feng, Yu Fu, Mao He,
JY Li, L. Xue, N. Zhang, XY Zhang
3
Physics of BTeV

• BTeV will vastly improve the constraints on the
  CKM anglesby making precision measurements of
  both the sides andthe angles a, b, g. ?
  over-constrain (r,h).
• Measurements and searches for rare and SM
  forbiddendecays ? Beyond the SM Physics.
• B factories will provide valuable input on
  sin(2b) and Vub,but they cannot compete with a
  hadron collider on measuringa, g, and searches
  for new physics (even by 2007). - They dont
  produce BS - s(bb) is 10,000X larger at the
  Tevatron than at U(4S)

4
B Production at the Tevatron
b cross section 100 mb at 2 TeV? 2x1011 bs
per 107 sec at L2x1032 cm-2 s-1.
5
B Physics Detector Wish List
Detector Property
Precision 3D Tracking
Excellent Particle ID(K, p, p, e, m)
Excellent calorimetry
Detached Vertex trigger at lowest level trigger
BTeV
?
?
?
?
6
The BTeV Detector
7
RICH Specifications

• Momentum Range of Interest p gt 2-3 GeV
  for CP tagging p lt 70 GeV ? clean
  separation of 2-body modes B?pp, Kp,
  KK.
• Minimize material in front of ECAL
• Longitudinal space available 3 meters
• Desirable to detect Cerenkov photons in the
  visible range (minimize chromatic error, less
  sensitive to contaminants, etc)
• ? Well-suited for a Ring Imaging Cerenkov
  Detector

Tagging kaons in BTeV Acc.
8
Radiators
Large momentum coverage requires a low index of
refraction ? gas radiatorWe chose C4F10
because heaviest gas which has high
transparency in the visible wide usage in
other HEP expts (e.g. Delphi, HERA-B,
HERMES, LHC-b). For momenta below 9.5 GeV/c
neither K nor P radiate in C4F10? Separate
liquid radiator for K/P separation below 9.5 GeV/c
9
The BTeV RICH
C5F12Liquid Radiator
Sphericalmirrors

• Photons from gasare reflected offmirrors and
  focused at the HPD plane.
• Photons from liquidare directly detected inthe
  PMTs.

C4F10 gasvolume
Arrays of163-channelHPDs(1000 in total)
PMT Arrays(5,000 in total)
10
Photon Angles
Liquid radiator photons are detectedin PMT array.
PMT Array
Gas radiator photons are detectedin HPD array.
Track fromInteraction
Gas RadiatorVolume
HPD Array
LiquidRadiator
Mirror
11
Gas Radiator
Gas C4F10 (n1.00138) K/p separation for
3 lt p lt70 GeV P/K separation for 9.5 lt p
lt 70 GeV

• Dqc(p-K) 0.43 mrad _at_ 70 GeV
• Must keep s(qC)/trk lt 0.13 mrad
• N(g) detected 65 (simulation)?Total
  uncertainty per photon must be kept below 1
  mrad.
• ? Requires 1.5 mm segmentation
• ? Well-suited for HPDs

No P/K separationbelow 9.5 GeV withgas alone
12
Detecting Gas Photonswith HPDs
g
-20 kV

• Started with 61-channel HPD that LHC-band DEP
  developed.
• We worked with DEP to develop 163-ch
  versionwhich would meet BTeVs requirements.
• Cross-focused onto hexagonal pixels
• Signal 5000 e- in Silicon.
• Readout system is being developed by Syracuse
  in collaboration with IDE AS Norway.

HPD
e
1.5 mm
163 channels
See talk by Ray Mountain
13
HPD Hexad
Mu-metalshield
Readout Boardsare mounted here
HPD
Full HPDArray
VA_BTEVASICs(ASD)
14
HPD Readout
VA_BTeVchip

• VA_BTeV ASIC being developed in collaboration
  with IDE AS Norway(independent from HPD
  development)
• Initial tests indicate that 500 e- noise level
  be achieved.
• Threshold for each channel is adjustable.
• Readout is binary (ON or OFF)
• Testing of first prototypes is underwayat
  Syracuse.

Readout Board
HPD
15
More on HPD Readout
Number of hit channels in consecutive beam
crossingsper 163 channels

• Discharge of FE chip requires 2 beam crossings,
  so a hit channel is dead for the next
  crossing.
• Simulated effect _at_ L2x1032 cm-2 s-1. Find
  lt10 loss of photons even in the busiest
  regions.(Much smaller elsewhere)

Y
HPD
X
HPD
16
Liquid Radiator
C5F12 (n1.24) Extends P/K separation
to plt9.5 GeV Extends K/p separation
into the plt3 GeV range

• Dqc(p-K) 5.3 mrad _at_ 9 GeVMust keep
  s(qC)/trklt1.7 mradN(g) detected 15
  (simulation)?Total uncertainty per photon must
  be kept below 7 mrad
• Separate PMT system (3 PMT is acceptable)

17
Detecting Liquid Photons -- PMTs
PMT Layout in BTeV
Mu-metalshields

• Expect to use 3 tubes.
• Shielding necessary ( B lt 15 G in PMT
  region)
• Expect
• s(qgc) 6 mrad, N(g)15/trk
• s(qtrkc) 1.6 mrad

3
18
Magnetic Shielding of PMTs
PMTs from 4 different manufacturers
B Trans.
Bmax15 G
Unshielded
Shielded
4.0
45.0
B Long.
Unshielded
Shielded
12.0
45.0
19
Preliminary Conceptual Tank Design
PMT Arrays
HPD Arrays
20
Liquid Radiator Conceptual Design

• 1 cm of C5F12
• 3 mm Carbon Fiber front window 3 mm quartz
  back window
• Split into 5 volumes to reduce pressure.
• Structure is reinforced by CF posts
• Total Material Budget X0 8.7
• Simulations indicate negligible impact on p0
  reconstruction since electrons from g conversions
  are only in a very weak magnetic field.

21
Progress with Mirrors

• Measurements being taken on the test bench
  of the TA2 group at CERN.
• Several mirrors under study
• COMPAS glass, glassfoam back.,
• CMA Carbon fiber
• Initial tests show that they meet spot size
  spec.

60 cm
Rcurv660 cm
Work being done byINFN Torino group
22
Expected Performancefrom Simulations
23
Efficiency vs Fake Rate
Gas Radiator HPDs

• Clean separationof B? pp from B?Kp and B?KKFor
  example
• e(B ? pp) 80 Kp Rejection 95 KK
  Rejection gt 99
• The latter is importantbecause Bs?KK lieson top
  of B?pp signal

B ? pp Simulationw/ 2 minimum biasevents.
Kp-
KK-
24
Low Momentum K/P separation using Liquid Radiator
PMTs
K and P cannot be separatedbelow 9.5 GeV/c in
gas system.Our simulations showed that we
could improve eD2 by 25 for BS and 10for B0
using liquid radiator.
Mom. lt 9 GeV/c
25
Expectations for eD2
Tag Type eD2 eD2
Tag Type B0 BS
Away Side Kaon Tag 6.0 5.8
Same Side Kaon (Pion) Tag 1.1 4.5
Away Side Muon Tag 0.8 1.3
Jet Charge 1.4 0.4
Total 9.2 12.1
BTeV Expected 10 13
Error on CP Asymmetry
26
Test Beam May 2003

• 15 HPDs to coverfull Cerenkov ring
• 100 GeV p beam
• Will measure resolution on Cerenkov
  angle photon yield
• Well also scan themirror to checksensitivity
• Construction underway.

HPD Enclosure
Front Entrance Window
Mirror Assembly
Concrete Support Blocks
27
Summary

• The BTeV RICH uses
• gas system C4F10 gas and HPDs, and
• liquid system C5F12 and PMTs
• to achieve excellent p/K/P separation for
  all relevant momenta less than 70 GeV/c.
• Recent addition of the liquid radiator system
  will improve eD2 for CP tag by 25 for BS and
  10 for B0.
• Initial tests of HPDs/PMTs look encouraging (see
  talk by R. Mountain)
• Test beam next year to validate detector design
  and simulations.

28
Why did we punt on Aerogel?
Low mult. event

• Both gas aerogel photons were detected in the
  HPDs
• After removing photons which were consistent
  with more than 1 track, aerogelprovided
  essentially no K/P separation
• The aerogel rings have too few photonsto
  compete with the bright gas rings

High mult. event
29
Alternate solution fordetecting gas
photons(MA-PMT16)

• Larger active region than 1st gen. ? lens
  system not required
• Viable backup to HPDs ? slightly worse position
  resolution..
• Currently being tested at Syracuse.