Hall A Collaboration Meeting 1

Neutron Transversity with BigBite + Super BigBite

C12-09-018

Andrew Puckett, LANLHall A Collaboration Meeting

6/10/11

6/10/11

Hall A Collaboration Meeting 2

Outline• Physics Motivation• Experiment Layout

– BigBite as e arm– SBS as h arm– High Luminosity 3He target

• Monte Carlo Simulation• Kinematic Coverage• Azimuthal Coverage• Projected Physics Impacts• Relation to Similar Experiments• Conclusions

6/10/11

Hall A Collaboration Meeting 3

Semi-Inclusive Deep Inelastic Scattering• In addition to usual DIS observables, SIDIS reaction N(e,e’h)X provides access to:• quark flavor• quark transverse motion• quark transverse spin

• Extra degrees of freedom relative to inclusive DIS more numerous and complicated structure functions • TMD approach: beyond collinear factorization, 8 leading-twist TMDs

6/10/11

Hall A Collaboration Meeting 4

SIDIS Kinematic Definitions• Incident (scattered) lepton four-momentum: l = (E,k), l’ = (E’,k’)• Scattered hadron four-momentum Ph = (Eh, ph)• Azimuthal angles defined according to Trento convention (right)

6/10/11

Hall A Collaboration Meeting 5

Transverse SSAs in SIDIS

Transverse target spin-dependent cross section for SIDIS

• Collins effect—chiral-odd quark transversity DF; chiral-odd Collins FF• Sivers effect—access to quark OAM and QCD FSI mechanism• “Pretzelosity” or Mulders-Tangerman function—access to wavefunction components differing by 2 units of OAM

Different TMD contributions isolated via azimuthal modulations

6/10/11

Hall A Collaboration Meeting 6

Physics of Transverse SSAs—Sivers Effect

6/10/11

• Sivers function is a correlation between kT of unpolarized quarks and nucleon transverse spin;• Connected to quark OAM• Generates left-right asymmetry in the SIDIS cross section (polarization normal to hadron production plane):

• Naive T-odd: presence requires a phase; generated (in SIDIS) by QCD FSI (Brodsky, Hwang, Schmidt) • Based on gauge invariance, QCD predicts sign change of Sivers function between SIDIS and Drell-Yan production• Needs experimental verification!

YD

qTSIDIS

qT ff

11

• Crucial test for TMD factorization approach to SSAs

Hall A Collaboration Meeting 7

Physics of Transverse SSAs—Collins Effect

6/10/11

• Transversity distribution expresses the correlation between quark and nucleon transverse polarization.• Accessible in SIDIS by coupling to spin-dependent Collins fragmentation function:

• For non-relativistic quarks, h1 = g1, difference between helicity and transversity is a signature of relativistic effects• First moment of h1 = tensor charge; calculable in lattice QCD

• Gluon transversity vanishes due to helicity conservation quark transversity is “valence-like”• Soffer bound:

Hall A Collaboration Meeting 8

Transversity and Collins FFs from SIDIS and e+e- Data

6/10/11

• NPB 191, 98 (2009): Phenomenological global fit of quark transversity distributions and Collins FFs to latest HERMES proton + COMPASS deuteron SIDIS data and BELLE e+e- data• Data favor opposite sign u and d quark transversity, constraints from pre-2007 data are limited• Latest fit favors h1

d close to Soffer limit.

u and d quark transversity Favored/Unfavored Collins FFs

Hall A Collaboration Meeting 9

Transversity and Collins FFs from SIDIS and e+e- Data

6/10/11

COMPASS deuteron Collins AUT HERMES proton Collins AUT

• Features: COMPASS data compatible with zero; HERMES data show clear non-zero signals, opposite sign between π+ and π- • Opposite sign of u and d transversity; • Favored and unfavored Collins FFs opposite sign, “unfavored” larger in magnitude!

Hall A Collaboration Meeting 10

Sivers Functions from SIDIS Data

6/10/11

• EPJ A, 39, 89 (2009)• Extraction and flavor separation of Sivers functions for all light-quark/antiquark flavors using phenomenological ansatz• u and d quark Sivers of opposite sign, similar magnitude • Large K+ Sivers moments appear to require a positive anti-s Sivers function• ubar, s, not presently distinguishable from zero• Negative dbar favored

Hall A Collaboration Meeting 11

Sivers Functions from SIDIS Data

6/10/11

HERMES and COMPASS data for Sivers AUT

Hall A Collaboration Meeting 12

Experiment C12-09-018—PAC Status

• Conditionally approved by PAC34– Technical/feasibility concerns including RICH operation, high-

rate tracking, trigger/DAQ, target upgrades, etc.• Returned to PAC37, largely satisfied PAC34 technical

concerns (we think). Approval still conditional on more detailed justification of physics impacts:– In the words of PAC37: “Return to PAC38 proving sufficient

statistics in multi-dimensional space”• PAC37 final report??? • Return to PAC38: Importance of first grading of SIDIS

proposals

6/10/11

Hall A Collaboration Meeting 13

Experiment C12-09-018 Collaboration

• Spokespeople:– Gordon Cates, UVA– Evaristo Cisbani, INFN– Gregg Franklin, CMU– Andrew Puckett, LANL– Bogdan Wojtsekhowski, JLab

• 100+ collaborators from ~30 institutions (so far)

6/10/11

Hall A Collaboration Meeting 14

Experiment C12-09-018—Run Plan• 40 (20) days production at E=11 (8.8) GeV on

transversely polarized 3He target• 65% target polarization• 4×1036 cm-2 s-1 en lumi.• Detect π±/π0/K± simultaneously in same

setting– RICH PID– Vertically symmetric acceptance

• SBS at 14 degrees as hadron arm• BigBite at 30 degrees as electron arm

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Hall A Collaboration Meeting 15

Experiment C12-09-018: Conceptual Layout

6/10/11

• Electron arm (BigBite) at 30° • Hadron arm (SBS) at 14°• Both arms: large solid angle and “infinite” momentum bite.• Upgraded high-luminosity 3He target, 60 cm long; target spin can be oriented in any transverse direction, we will use 8 to cover full azimuthal phase space• 10X larger angular acceptance compared to 6 GeV transversity

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Hadron arm: Super BigBite Spectrometer (SBS) • http://hallaweb.jlab.org/12GeV/SuperBigBite/• Warm dipole magnet 48D48, Bdl = 2 Tm; cut in yoke for passage of beam pipe, reach to very forward angles. (Lambertson magnet, familiar concept in accelerator physics).

Detectors for SIDIS• GEMs: high-rate capability, high-resolution tracking; momentum/angle/vertex/RICH, resolution• HCAL: Iron-scint hadronic calorimeter; trigger + timing + coordinate measurement+reduce search area for high-rate tracking, AND π0 detection!• HERMES RICH: Hadron PID, full π/K/p separation 2 GeV<p<15 GeV

Hall A Collaboration Meeting 17

SBS Acceptance Studies (GEANT)

6/10/11

• Top left: solid angle vs. momentum/vertex• almost constant, average = 40 msr

• Top right: 2D correlations: angles, momentum, vertex (almost “boxlike”)• Bend angles vs. p for upbending and downbending particles, at 2.0 Tm field integral

Hall A Collaboration Meeting 18

The HERMES RICH Detector

6/10/11

5.5 GeV K+

14.6 GeV e-1.5 GeV p-

REAL DATA from NIMA 479 (2002) 511

• Full π/K/p separation (2 GeV < p < 15 GeV) based on dual-radiator (gas+aerogel) design• High segmentation (1,934 PMTs) = excellent resolution and high-rate capability• ~5 cm aerogel n=1.0304• C4F10, n = 1.00137• Operation in up to 90 G stray field in HERMES—expect similar or lower in SBS

Status• 1 detector, both aerogels from HERMES in storage @ UVa• Prototype construction underway @ W&M, with additional 64 PMTs

Hall A Collaboration Meeting6/10/11 19

Electron arm: BigBite Spectrometer• Already used successfully in a large number of experiments, including E06-010 (transversity)

Detectors for SIDIS• Lead-glass preshower/shower for trigger and offline pion rejection; threshold = 1 GeV• GEM chambers (INFN) instead of MWDC: • Increase rate capability in high-luminosity environment• Improve resolution

• Gas Cherenkov: trigger and pion rejection• Charge tagger: possible supplement to GC for neutral trigger suppression

Hall A Collaboration Meeting 206/10/11

BigBite Spectrometer

• 1.2 Tesla dipole magnet in front of detector stack• Positioned to subtend ~64 msr solid angle• Demonstrated performance at same angle/distance setting in E06-010• Upgrade to GEM tracking to increase rate capability for higher luminosity and resolution at higher momenta• Upgrade gas Cherenkov (to working status) for improved trigger and electron PID

Hall A Collaboration Meeting 216/10/11

• History of FOM increases in JLab polarized 3He experiments (top right)• New design with convection-driven flow • Fast replacement of polarized gas • Tolerate higher beam currents—support

up to 60 μA, 60 cm long cell• 4 × 1036 cm-2 s-1 en luminosity• Decouple location of target chamber and

pumping chamber; decouple magnetic field directions

• Concept already demonstrated in bench tests• Fast spin orientation: ~every 2 minutes• Metal target cell in vacuum: reduce non-3He material on beamline—reduce background rates

High Luminosity Polarized 3He Target

Schematic of target chamber in vacuum Bench test of convection flow

Hall A Collaboration Meeting 22

Monte Carlo Simulation• Physics event-generator + acceptance/resolution model only; no detector

response yet• Physics:

– CTEQ6 PDFs– DSS2007 FFs– Anselmino et al. Collins and Sivers effects

• Generated large-statistics pseudo data set– Analyze to demonstrate extraction procedure (MLE)– Calculate statistical error

• BigBite model: realistic acceptance/resolution calculations calibrated to E06-010 data

• SBS model: “box” acceptance (detailed acceptance studies were not done by the time of the large simulation run, “box” acceptance is a good approximation)

6/10/11

Hall A Collaboration Meeting 236/10/11

• 1D kinematic distributions (cross-section and acceptance-weighted)• Cover the valence region (0.1<x<0.7) at high Q2

• We can also cover down to lower x @ 1< Q2 with pre-scaled, low-threshold BigBite trigger, large cross section only need a fraction of the triggers.

• Cover the current fragmentation region (0.2<z<0.7)• Cover the most interesting pT range: large enough for non-zero asymmetries; small-enough that we believe TMD factorization is valid

Hall A Collaboration Meeting 246/10/11

Q2, x, z, pT coverage vs. x

Two beam energies for ~2 GeV2 lever arm in Q2 at same x!

Hall A Collaboration Meeting 25

C12-09-018, E=11 GeV

C12-09-018, E=8.8 GeV

E06-010, E=5.9 GeV

6/10/11

More on Q2-x Coverage

Hall A Collaboration Meeting 266/10/11

W, W’ and y coverage vs. x

Hall A Collaboration Meeting 276/10/11

• Polar pT, ϕ plots, left to right = hadron angle, target angle, Collins angle, Sivers angle• Integrated over x, z• 8 target spin orientations: ±horizontal ±vertical, ±45°, ±135°.• Full ϕS angle coverage and ~50% ϕh coverage should allow reliable extraction of nearly all allowed Fourier moments with well-controlled systematics and minimal increase in error

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• Same as previous slide, with Cartesian representation

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Increasing z

Incr

easi

ng x

Hall A Collaboration Meeting 306/10/11

Increasing z

Incr

easi

ng x

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Increasing z

Incr

easi

ng x

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Increasing z

Incr

easi

ng x

Hall A Collaboration Meeting 33

PROJECTED PHYSICS RESULTS & IMPACTS

6/10/11

Hall A Collaboration Meeting 34

3He Asymmetries: MLE Extraction

6/10/11

• Two-term extraction of Collins and Sivers moments: linearized maximum-likelihood (weighted sum) estimators. • Symmetry of acceptance in target-spin dependent azimuthal angles cancels acceptance effects to first order (Besset et al., NIM 166, 515 (1979))•

• θS is the polar angle between target spin and virtual photon direction (since target spin is perp. to beamline, θS is slightly different from 90°

• Method can be expanded to arbitrary number of Fourier moments with reduced precision

Hall A Collaboration Meeting 35

Validity of Extraction Method

6/10/11

• Helium-3 pi+ Sivers asymmetries, 2D binning in x and z, E = 11 GeV• Only 1/2 of expected statistics!• Points = extracted asymmetry• Curves = model asymmetry input to Monte Carlo

Typical (x,z) bin: 3He asym. error = 0.06% (absolute)!

Hall A Collaboration Meeting 36

Projected Neutron Precision, Recall:

6/10/11

~87% ~8% ~1.5%

Polarized 3He as effective polarized neutron target

Effective nucleon polarization approach:

Scopetta, PRD 75, 054005 (2007)

~12 μA, 10 atm 3He = ~1036 cm-2s-1 en luminosity

Hall A Collaboration Meeting 37

Comparison to Best Current Knowledge

6/10/11

• HERMES/COMPASS published Sivers moments in 1D x binning—compared to our projected results, 1D binned x• Neutron predictions and uncertainty bands from Prokudin (Torino/Anselmino group)• Bands represent uncertainty in neutron from HERMES proton/COMPASS

deuteron within a specific model; properly folded with our kinematics/acceptance.• In reality, the high-x region is totally unknown—results from pp suggest

more flexible parametrizations may be needed

1D binned neutron precision ~0.2%

Hall A Collaboration Meeting 38

Neutron Sivers Moments in 6x6 x, pT Bins

6/10/11

• Some correlation between x, pT in our acceptance but good precision in wide two-dimensional coverage: Asymmetries at large pT could be as large as 20-50%!!!

Typical Error ~0.5%

Hall A Collaboration Meeting 39

Shrinking the Error Corridors

6/10/11

• A. Prokudin generously ran a small subset of our projected results through Torino group’s global fit machinery; π+ Sivers moments at E = 11 GeV. • Left: >5X shrinking of n(e,e’ π+)X Sivers AUT band• Right: reducing the uncertainty in d quark Sivers in six-flavor extraction• Experiment will provide π±/π0/K± at similar precision (Kaon errors 2-3X pion errors) for both E = 8.8 GeV and E = 11 GeV Collins/Sivers (and Pretzelosity)

Hall A Collaboration Meeting 40

Collins Moments—1D Comparison

6/10/11

• Existing Collins parametrization predicts generally small (few-% level) neutron asymmetries. This makes the measurement of transversity very difficult cf. Sivers!• Parametrization enforces Soffer bound on d quark transversity distribution• Some kinematic suppression of asymmetry due to large y

• If Soffer bound is violated, as suggested by some theorists and by E06-010 data at ~2σ level, asymmetries at large x could be substantially larger.

Typical Error ~ 0.2%

Hall A Collaboration Meeting 41

Collins Moments: 2D 5x6 x, z bins

6/10/11

Typical Error ~0.5%• Almost completely uncorrelated x, z coverage • Independently

constrain Collins FF• ~10-30% accuracy for 2D kinematic bins relative to this model

Hall A Collaboration Meeting 42

Comparison to Other Experiments

6/10/11

• Crude Comparison of FOM between different 3He experiments• Relative asymmetry uncertainty squared ~ N events × A2

Factor SOLID SBS+BB Commentf 0.15-0.3 0.15-0.3 same (physics)

PT 0.65 0.65 same (SEOP)

ΔΩe ×ΔΩh = ΔΩ 0.416×0.0955 = 0.040

0.064×0.040 = 0.0026

SOLID/SBS ~ 15

Luminosity 10 atm @ 15 uA 10 atm @ 40-60 uA (GEn-II target design)

SOLID/SBS ~ 0.25

Lumi × Solid Angle SOLID/SBS ~ 4-6

σ at x = 0.5, <Q2> ~ 5.5 GeV2

at x = 0.5, <Q2> ~ 8 GeV2

Low Q2 = higher σ SOLID=forward-angle

Hall A Collaboration Meeting 43

SBS vs. SOLID phase space after SIDIS cuts

6/10/11

• At 11 GeV, SBS+BB has significantly higher x, Q2 reach (complementary), lower counting rate due to large angles, large Q2

• pT coverage: SBS has similar or greater high-pT coverage; less low-pT coverage at small x

Hall A Collaboration Meeting 44

SBS/BigBite and SOLID: Our Perspective• SBS+BB SIDIS will advance experimental knowledge of SIDIS SSA for

charged and neutral pions and kaons, by at least a factor of 10 wrt current knowledge (~100X stats. of HERMES), at low incremental cost relative to approved form factor program, and on a relatively fast timeline

• Apart from SBS+BB, virtually no SIDIS data between now (E06-010) and SOLID*

• Large parallel effort in transverse spin physics in Drell-Yan and pp at RHIC/FNAL/etc. in the next few years

• SOLID will perform the “ultimate” fully differential kinematic binning @ 12 GeV (for π±), but presumably after SBS form factor program and Möller (long timeline)

• C12-09-018 will help to advance this field, by providing urgently needed precision data, in a timely fashion, taking us “halfway” to the “ultimate” experiment, and with complementary kinematic coverage

6/10/11

* COMPASS will publish update with ~2X current stats, CLAS12+HDice could provide proton data

Hall A Collaboration Meeting 45

Conclusions• SBS+BB is a natural configuration for SIDIS experiments,

similar in many respects to the HERMES experiment, but at ~105 higher luminosity

• Based on PAC37 recommendations, a significant physics simulation and analysis effort, along with theory support, has been performed to quantify the physics impact of C12-09-018 as clearly as possible.

• Physics impact is now quite clear and “there for the taking”• Fits naturally into the 12 GeV JLab SIDIS program• We will return to PAC38 to seek full approval and grading

6/10/11

Hall A Collaboration Meeting 46

BACKUP SLIDES

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Hall A Collaboration Meeting 476/10/11

Unique Advantages/Complementarity of Halls A/B/C for SIDIS Experiments @ JLab: Our View

Hall A• Polarized neutron measurements >1037 cm-2s-1

• Transverse/longitudinally polarized 3He targets @ high luminosity; • Large acceptance, open-geometry spectrometers• High-quality PID

Hall B• Polarized proton measurements; • Longitudinal/transverse proton targets at max. luminosity of CLAS12 ~1035 cm-2s-1

• Very large acceptance• Many-dimensional phase space• Provide information on closely related mechanisms, e.g. vector meson production

Hall C• Precision unpolarized cross section measurements w/ magnetic spectrometers• Require lower statistics compared to asymmetries• proton/deuteron• L/T separation• Understand SIDIS reaction mechanism

Hall A Collaboration Meeting 48

C12-09-018 Collaboration I

6/10/11

G. Cates(spokesperson), H. Baghdasaryan, D. Day, P. Dolph,N. Kalantarians, R. Lindgren, N. Liyanage, V. Nelyubin, Al Tobias

University of Virginia, Charlottesville, VA 22901E. Cisbani(spokesperson), A. Del Dotto, F. Garibaldi, S. Frullani

INFN Rome gruppo collegato Sanita and Istituto Superiore di Sanita, Rome, ItalyG.B. Franklin(spokesperson), V. Mamyan, B. Quinn, R. Schumacher

Carnegie Mellon University, Pittsburgh, PA 15213A. Puckett (spokesperson), X. Jiang

Los Alamos National Laboratory, Los Alamos, NM 87545B. Wojtsekhowski (contact and spokesperson), K. Allada, A. Camsonne, E. Chudakov,

P. Degtyarenko, M. Jones, J. Gomez, O. Hansen, D. W. Higinbotham,J. LeRose, R. Michaels, S. Nanda, L.Pentchev, A. Saha

Thomas Jeerson National Accelerator Facility, Newport News, VA 23606J. Annand, D. Hamilton, D. Ireland, R. Kaiser, K. Livingston,

I. MacGregor, B. Seitz, and G. RosnerUniversity of Glasgow, Glasgow, Scotland

Hall A Collaboration Meeting 49

C12-09-018 Collaboration II

6/10/11

W. Boeglin, P. Markowitz, J. ReinholdFlorida International University, Fl

T. AverettCollege of William and Mary

M. Khandaker, V. PunjabiNorfolk State University

S. RiordanUniversity of Massachusetts Amherst, Amherst, MA 01003

D. Nikolenko, I. Rachek, Yu. ShestakovBudker Institute, Novosibirsk, Russia

M. CapogniINFN Rome gruppo collegato Sanita and ENEA Casaccia, Rome, Italy

F. Meddi, G. Salme, G.M. UrciuoliINFN Rome and “La Sapienza" University, Rome, Italy

S. ScopettaUniversity of Perugia and INFN Perugia, Perugia, Italy

G. De Cataldo, R. De Leo, L. Lagamba, S. Marrone, E. NappiINFN Bari and University of Bari, Bari, Italy

Hall A Collaboration Meeting 50

C12-09-018 Collaboration III

6/10/11

R. PerrinoINFN Lecce, Lecce, Italy

V. Bellini, A. Giusa, F. Mammoliti, G. Russo, M.L. Sperduto, C.M. SuteraINFN Catania and University of Catania, Catania, Italy

M. Aghasyan, E. De Sanctis, D. Hasch, V. Lucherini, M. Mirazita, S.A. Pereira, P. RossiINFN, Laboratori Nazionali di Frascati, Frascati, Italy

A. D'Angelo, C. Schaerf, V. VegnaINFN Rome2 and University \Tor Vergata", Rome, Italy

M. Battaglieri, R. De Vita, M. Osipenko, G. Ricco, M. Ripani, M. TaiutiINFN Genova and University of Genova, Genoa, Italy

P.F. Dalpiaz, G. Ciullo, M. Contalbrigo, P. Lenisa, L. PappalardoINFN Ferrara and University of Ferrara, Ferrara, Italy

Hall A Collaboration Meeting 51

C12-09-018 Collaboration IV

6/10/11

J. Lichtenstadt, I. Pomerantz, E. PiasetzkyTel Aviv University, Israel

G. RonHebrew University of Jerusalem, Jerusalem, Israel

A. GlamazdinKharkov Institute of Physics and Technology, Kharkov 310077, Ukraine

J. Calarco, K. SliferUniversity of New Hampshire, Durham, NH 03824

W. Bertozzi, S. Gilad, V. SulkoskyMassachusetts Institute of Technology, Cambridge, MA 02139

B. VlahovicNorth Carolina Central University, Durham, NC 03824

A. SartySaint Mary's University, Nova Scotia, Canada B3H 3C3

K. Aniol and D. J. MagaziotisCal State University, Los Angeles, CA 90032

S. Abrahamyan, S. Mayilyan, A. Shahinyan, H. VoskanyanYerevan Physics Institute, Yerevan, Armenia

Hall A Collaboration Meeting 52

Concerns in PAC34 Report: Appendix B

6/10/11

1) Can a combination of beam tests and fully realistic simulations demonstrate the feasibility of running the experiment at the proposed luminosity? 2) Will the very high rates affect the ability to extract relatively small spin asymmetries accurately? 3) Would a better coverage at smaller hadron angles, perhaps combined with running at lower luminosity, give a better overall result (due to better coverage in pt, θpq and φ*). 4) Is it possible to add some (limited) π0 detection to enhance the physics output of the proposal? 5) Is a z cut of 0.2 too low for JLab kinematics? 6) What will the effect of diffractive vector meson production be on the extraction of SIDIS structure functions? 7) What is the impact of radiative tails from exclusive and resonance region scattering on the structure function extraction? (In particular, will the cross sections and spin asymmetries of these regions be sufficiently well known?) 8) Can the possibility of polarized proton and deuteron targets to obtain neutron structure functions be considered and integrated into a comprehensive program at JLab?

• Yes: Slides 22-23 and 41-50, Proposal Chapter 3 Sections 3.1-3.4

• No: backup slides 35 and 41-50, proposal sections 3.1-3.4 and 5.6• Transversity kinematics optimized with h arm centered at non-zero pT

• Yes: π02γ acceptance ~70% of charged π acceptance, existing HCAL• Presented in proposal appendix B• Small, proposal section 5.6.3 and backup slide • Very small and exclusive (z=1) is in our acceptance (large momentum acceptance)

•See slide 29, 3He is clear advantage for Hall A: BB&SBS

Hall A Collaboration Meeting 53

2.5 GeV π

2.5 GeV K

Trackless background

ring

6/10/11

Monte Carlo of HERMES RICH

• Soft photon background rate for RICH operation major concern of PAC34• Magnet shields charged particles p<1 GeV; • Beamline is a major source of background; add lead shielding.• Low energy photonsCompton, pair-prod. of secondary e-/e+ in aerogel• GEANT calculation of background rate in aerogel: MCWORKS/DINREG• Validated by data in many experiments• Analytic calculation of Cherenkov yield• Ray-tracing Monte Carlo.

GEANT layout with planned beamline shielding

MC 1-event display, 10 ns TDC cut, full lumi.

Target

48D48

Aerogel

PMTs HCAL

Pb shielding

Average of ~2 background-induced accidental PMT hits

per event

Hall A Collaboration Meeting 546/10/11

SBS RICH GEANT simulation:

• PAC34 main concern: feasibility of operating SBS RICH at proposed lumiGEANT simulation• GEANT validated by comparing to existing data from BigBite—backup slides 41-50:• MWDC rates• BB GC PMT rate

• Neutron-induced rate is negligible fraction of total—backup slides• Dominant backgr. = Compton electrons produced in aerogel • Results: ~10-3 average PMT occupancy for RICH w/TDC readout and 10 ns (offline) window• Pb-pipe beamline shielding reduces rate by 2X on avg. mostly from small-angle side• Average S:N ≥ 100:1 • 50X safety factor for RICH; i.e., even with 50×GEANT rate, we are at 5% occupancy, which is still a good operating condition.

Beamline Pb Pipe/Blanket? No YesAerogel rate (kHz/PMT) 111 65

Glass+Quartz direct rate 28 17

Total rate 139 82

Occupancy (Δt = 10 ns) (%) 0.139 0.082

With Pb pipeWithout Pb pipe