Beam Background overview Hiroyuki NAKAYAMA (KEK) th B2GM This talk covers details of background sources. The other talk on Wednesday will mainly summarize today’s sub-detector results.

“Crisis” at the last B2GM Gammas in background shower reach quartz bar and generate electrons by Compton scattering and etc.. Those electrons emit Cerenkov photons and those photons reach PMT photocathode. TOP PMT p.e. flux (M. Petric, March 2012) Requirement: 1MHz/PMT 2 RBBs have been found to be overestimated due to the bug - CDC wire hit rate, ECL fake clusters/pile-up noise - Radiation dose on ECL crystals - Neutron rate on ARICH HAPD, CDC readout board, ECL diodes In addition, need to be mitigated

What’s new since the last B2GM The major updates since the last B2GM (2nd campaign) are following: -Thick tungsten shield inside QCS cryostat -Neutron shield (ARICH: polyethylene+30%boron, CDC EB: B 4 C) -Accelerator tracking for RBB samples are updated with bug-fixed transverse momentum, realistic beam-beam kick -Touschek samples are updated with latest version of optics and updated collimator settings -LER upstream aperture around z=20cm is widened to reduce Touschek loss there (which might increase LER SR: see Yuri’s talk) -No change on Coulomb input files Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 3

RBB bugs found in optics simulation after B2GM Beam angular divergence was too large. – Beam loss rate was overestimated Loss rate : 3.47GHz  2.23GHz (correct) Loss wattage: 0.43W  0.25W (correct) Transverse momentum was too large. – BG phi-dependence was too sharp. – Sqrt(p x 2 +p y 2 ) : ~0.3GeV  ~0.03 GeV (correct) Funakoshi The last B2GM correct Px,Py Sqrt(P x 2 +P y 2 )[GeV] P total [GeV] 4 P T >P total ??

QCS geometry implemented in GEANT4 By Dmitri Liventsev tungsten 5 Wider cryostat body allows more shield inside. As a drawback, there are less space btw CDC and QCS for cables, cooling pipes, etc.. (needs to be accessed)

TOP background by RBB_HER new QCS vs. old QCS TOPSimHits/bar/5us TOP requirement: 1MHz/PMT = 800 TOPSimHits/bar/5us for sum of all BG - Loss at z>100cm are well shielded - Loss at z<100cm remains - Loss at z>100cm are well shielded - Loss at z<100cm remains Loss position of beam electrons which cause TOP hits 6 TOP bar ID z[cm] 外 上 内 下 外 Nakayama TOP BG

Neutron shield inside ARICH structure Hiroyuki Nakayama (KEK) 11th B2GM (Mar , 2012) 7 6cm thick polystyrene proposed by ARICH group Preliminary! Not invading cable space

Neutron shield in CDC structure Hiroyuki Nakayama (KEK) 11th B2GM (Mar , 2012) 8 B4CB4C B 4 C shield just inside CDC inner cover, proposed by CDC group Preliminary! Not invading cable space

RBB_HER and QC1RP leak field 9 W x-z plane e- LER QC1 leak field HER QC1 HER QC2 e- W x-z plane e- LER QC1 leak field HER QC1 HER QC2 e- tungsten

TOP background by RBB_HER without leak vs. with leak TOP requirement: 1MHz/PMT = 800 TOPSimHits/bar/5us for sum of all BG (new QCS) Canceling leak field at z~1m seems not necessary for TOP BG, because showers at z>1m are anyway stopped by QCS tungsten shield (How about neutrons?) 10 Loss position of beam electrons which cause TOP hits TOPSimHits/bar/5us TOP bar ID z[cm] 外 上 内 下 外 Nakayama TOP BG tungsten

TOP background Touschek LER(narrow) vs RBB_HER (new QCS) 11 RBB_HER -w/o cancelled -w/ beam-beam kick TOPSimHits/bar/5us TOP bar ID z[cm] 外 上 内 下 外 Touschek loss at z=20cm should also be reduced. Nakayama TOP BG

LER Touschek loss(narrow) at z=~20cm 12 Group A Group B Group C e+e+ HER e- beam LER e+ beam z[m] x[m] Widening LER upstream aperture can reduce LER Touschek loss, but increase SR from LER. With wider aperture, Group A are lost IP downstream, but part of Group B/C will be still lost IP upstream Touschek LER loss position

Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 13 Radius of this part is widened from 2.82mm to 5.82mm

3 rd MC campaign Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 14

Data samples for 3 rd MC campaign IR loss rateEnergy#event RBB_LER5.55 GHz0-2GeV110,883 RBB_HER2.28 GHz0-2GeV45,554 Touschek_LER0.248 GHz~4GeV5,162 Touschek_HER0.031 GHz~7GeV617 Coulomb_LER0.09 GHz4GeV1800 Coulomb_HER0.001 GHz7GeV20 timesize 90min3.3GB 100min2.7GB 60min1.8GB 10min0.3GB 25min0.5GB 4min0.01GB KEKCC:~nakayama/basf2_opt/release_201207_MCgen/Work_MCgen/output/*.root 20us * 10 files for each background sources: {Touschek/Coulomb/RBB}_{HER/LER} Statistics for 20us files You can find merged files (by hadd command) which correspond to 200us each at KEKCC:~nakayama/basf2_opt/release_201207_MCgen/Work_MCgen/hadd/*.root Toolkit for those who need to generate by themselves: KEKCC:~nakayama/basf2_opt/release_201207_MCgen/Work.tgz Revision 3290, bfield:1.5T

LER (4GeV e+)HER (7GeV e-) Rad. Bhabha0.45 W (eff. 0.7GHz)0.28W (eff. 0.24GHz) Touschek0.16 W (0.25GHz)0.03 W (0.03 GHz) Coulomb0.06 W (0.09GHz)0.001W (0.001GHz) Total BG (for 3 rd MC campaign) 1GeV,1GHz = 0.16W HER (e-) LER (e+) Ver Loss wattage = loss rate * energy of loss particle Loss wattage = loss rate * energy of loss particle 16

LER (4GeV e+)HER (7GeV e-) Rad. Bhabha0.45 W (eff. 0.7GHz)0.44W (eff. 0.40GHz) Touschek0.10 W (0.16GHz)0.05 W (0.04GHz) Coulomb0.06 W (0.09GHz)0.001W (0.001GHz) Total BG (for 2 nd MC campaign) 1GeV,1GHz = 0.16W L- side R- side Hiroyuki Nakayama (KEK)17 11th B2GM (Mar , 2012) Ver Cf. 1 st campaign LER Touschek 0.9GHz z = +1m Cf. 1 st campaign LER Touschek 0.9GHz z = +1m obsolete

RBB HER (electrons) w/ leak + realistic beam-beam CoordinateBeamLoss2012_6_12_14_50_48.dat ? event herfqlc5424b_st 0.28W GHz W x-z plane e- LER QC1 leak field HER QC1 HER QC2 e-

RBB_LER(positrons) w/ realistic beam-beam CoordinateBeamLoss2012_6_12_17_17_45.dat ? event 0.45W GHz e+

Touschek LER MHz 265MHz |s|<4m - 14MHz from Fuji - 140MHz from ss=2910m - 80MHz from ss=2990m - 14MHz from ss=2997m - 3.5MHz from ss>3001m (lost at |s|<60cm) 265MHz |s|<4m - 14MHz from Fuji - 140MHz from ss=2910m - 80MHz from ss=2990m - 14MHz from ss=2997m - 3.5MHz from ss>3001m (lost at |s|<60cm) LER_2012_06_22_11-26.data5.tab Updated collimator settings w/ widest LER aperture 20 MHz e+ sler_1672_5

Touschek HER MHz 30MHz |s|<4m - 7MHz from s~500m - 26MHz from s<40m 30MHz |s|<4m - 7MHz from s~500m - 26MHz from s<40m HER_2012_07_04_10-17.data5.tab Updated collimator settings 21 sher_5745_1 e-

Beam-gas Coulomb LER,HER Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 22 lerfqlc_1604/herfqlc5605 Should be updated LER HER e+ e- 90MHz 1MHz Same as 2 nd -campaign Very sensitive for collimator width “Hand-calculation” based on

Event displays Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 23

Event display(all BG) Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) ns Showing E>1MeV Green: neutron Yellow: gamma Red: e-, Blue: e+ ▲ : primary loss position cm RBB+Touschek+Coulomb

Event display (Touschek LER) Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) ns Showing E>1MeV Green: neutron Yellow: gamma Red: e-, Blue: e+ ▲ : primary loss position cm

Event display (RBB HER) Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 26 More figures incl. event-by-event ones  More figures incl. event-by-event ones  100ns Showing E>1MeV Green: neutron Yellow: gamma Red: e-, Blue: e+ ▲ : primary loss position cm

Touschek LER (event #11) Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 27 cm Usually loss at z=1cm are well shielded by QCS tungsten shield Event-by event

Touschek LER (event #12) Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 28 cm Sometimes beam particles lost at z=1cm are tip-scattered and moving forward and generate shower closer to IP, which might be VTX/TOP background Event-by event

Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 29 Touschek_LER RBB_HERc Further mitigation possibilities: - SVD support structure is not implemented in GEANT4. - QCS cryostat head might be made by Tungsten, not SUS. Further mitigation possibilities: - SVD support structure is not implemented in GEANT4. - QCS cryostat head might be made by Tungsten, not SUS. Touschek_LER, RBB_HER are Loss at z=0~0.6m

What is NOT included now Background from beam loss at |z|>4m – Especially important for end-cap detectors – Dmitri is implementing tunnel geometry Secondary showers from collimator – So far perfect collimation is assumed – Tip-scattered beam particle might escape and might enter IR Detailed SR check – ridge optimization/ tip-scattering, miss alignment, etc.. BG during injection BG situation at the day-1 (detuned optics, bad vacuum) Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 30

Summary We performed 3 rd background MC campaign TOP-PMT BG seems less severer (bug-fix, QCS tungsten shield) Tungsten shield stops showers but generates more neutrons: should be checked carefully (ARICH HAPD,CDC EB, ECL, etc..) SR with LER wider aperture should be confirmed to be safe  Decision of QCS-R dipole-cancelation in this meeting Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 31 Now let’s hear from each sub-detector - Estimated background level? - Hardware requirement (incl. recent irradiation test) - Safety factor?

Backup Hiroyuki Nakayama (KEK) B-suishin (June 7, 2012) 32

Detector performance SimulationRequirement PXD occupancy 0.64% (2-photon) % (Touschek LER) < 3% SVD occupancy ~4% (z) / 7% (r-phi) assuming 5000e- threshold and 50ns shaping time < ~10% CDC hit rate 280kHz/wire< 200kHz/wire TOP K/pi separation K/pi separation remains good TOP photo- cathode aging Photoelectron flux: 20MHz/PMT <1MHz/PMT ECL16 fake clusters in 100ns time window 11 MeV pile up noise in f-endcap Belle1: 6 fake clusters Belle1: 0.8 MeV pile up BKLM Need to replace layer 0 and 1 with scintillator. It also recovers efficiency of layer 2 (0.66->0.91), layer 3(0.78->0.94) EKLM Strip occupancy: 20kHz < 200KHz  2.2 clusters, 3MeV(3cm W)  ?(3cm W)  3MHz/PMT(3cm W) Mar. 2012

Hiroyuki Nakayama (KEK) 11th B2GM (Mar , 2012) 34 Neutron flux Region Simulation [ x10 11 eqn/cm 2 /year ] R&D assumption [ x10 11 eqn/cm 2 /year ] Current tolerance PXD DHP,DCD, Swithers 110 OK up to 100 x10 11 eqn/cm 2 SVD Sensors, chips 10- Should be OK, irradiation test ongoing CDC Readout Boards 41 Tested up to 10 x10 11 eqn/cm2 TOP Readout electronics Tested up to 10 x10 11 eqn/cm2 ASIC not tested yet ARICH HAPD 2.5 (inner rings) 0.4 Tested up to 4 x10 11 eqn/cm2 Start to see degradation ECL Crystals OK up to 100 x10 11 eqn/cm2 ( by Kuzmin ) ECL Diodes 1.8 (f-endcap) 1 OK up to 10 x10 11 eqn/cm2 (by Kuzmin, dark current increased BKLM SiPMs year = 10 7 sec 1MeV equivalent rate  0.9(3cm W)  1(3cm W +6cm Poly)  ?(3cm W+ B 4 C) Mar. 2012

Hiroyuki Nakayama (KEK) 11th B2GM (Mar , 2012) 35 Radiation dose Region Simulation [Gy/year] R&D assumption [Gy/year] Current tolerance PXD Sensor 19k>19k Tested up to 100kGy(=10Mrad) 200kGy would be also OK SVD APV 3k10k OK up to 100kGy (by Peter) CDC Readout boards Tested up to 1000Gy New SFP survive w/o communication TOP Readout electronics 730 Tested up to 300Gy for FPGA and optical transceiver/fiber, ASIC not tested yet ARICH HAPDs APD tested up to 1000Gy ECL Crystals 41 (fwd-endcap) 10 OK up to 100Gy (by Kuzmin) (TDR said 36Gy) ECL Diodes 35 (fwd-endcap) 70 OK up to 700Gy (by Kuzmin) BKLM SiPMSafe (Piilonen) -- EKLM SiPMSafe (Timofey) -- 1 year = 10 7 sec 1krad=10Gy 10krad=100Gy 100krad=1000Gy  2.5(3cm W) Mar. 2012

TOP-PMT photocathode lifetime  Gammas in background shower reach quartz bar and generate electrons by Compton scattering and etc.. Those electrons emit Cerenkov photons and those photons reach PMT photocathode. M. Petric, March 2012 Requirement: 1MHz/PMT 36 RBBs have been found to be overestimated due to the bug - CDC wire hit rate, ECL fake clusters/pile-up noise - Radiation dose on ECL crystals - Neutron rate on ARICH HAPD, CDC readout board, ECL diodes In addition, need to be mitigated

Process which is responsible for beam losses due to RBB HER – Beam angular divergence original angular divergence (due to beam emittance) angle change due to Bhabha scattering/ beam-beam kick – Kick by Belle solenoid field Mainly vertical but we have to consider a resultant horizontal kick – Dipole kick by leakage field from LER QC1RP Kick angle is about 1.3mrad for 7GeV particles. The kick might be canceled by installing a permanent dipole magnet or a compensation SC coil.  Big impact on QCSR design Funakoshi 37

Wider cryostat body allows more shield inside. As a drawback, there are less space btw CDC and QCS for cables, cooling pipes, etc.. Ohuchi, 2012/3/26 Tungsten shield in QCS cryostat t86 t69 38 tungsten Tungsten shield is also added inside L-side cryostat (a concrete design being assessed) R-side cryostat

More tungsten shields? Hiroyuki Nakayama (KEK) 11th B2GM (Mar , 2012) 39 Recently proposed by Uno-san We had similar shields in Belle-I Space issue? Who support the weight? Discussion just started VERY Preliminary!

Touschek LER loss rate D03H1 D03H2 D01H1 D01H2 D01H3 D01H4 D03V1 D03V2 D01V1 D06H1 D06H2 D06H3 D06H4 D06V1 D06V2 427GHz total loss <~70GHz each collimator ~3.5GHz the last collimator (D01H4) 0.25GHz |s|<4m LER_2012_06_22_11-26.data5.tab e+