Strawman Detector F Forti Universit and INFN Pisa

Strawman Detector F. Forti, Università and INFN, Pisa UK Super. B Meeting Daresbury, April 26, 2006 April 27, 2006 F. Forti - Super. B Strawman Detector

Experimental issues • Babar and Belle designs have proven to be very effective for B-Factory physics – Follow the same ideas for Super. B detector – Try to reuse same components as much as possible • Main issues – Machine backgrounds – Beam energy asymmetry – Strong interaction with machine design • Impact on – Detector segmentation – Radius of beam pipe and first sensitive layer – Radiation hardness April 27, 2006 F. Forti - Super. B Strawman Detector 2

The BABAR Detector 1. 5 T solenoid EMC 6580 Cs. I(Tl) crystals e+ (3. 1 Ge. V) DIRC (PID) 144 quartz bars 11000 PMs e- (9 Ge. V) Drift Chamber 40 stereo layers Instrumented Flux Return iron / RPCs&LSTs ( / neutral hadrons) Silicon Vertex Tracker 5 layers, double sided strips SVT: 97% efficiency, 15 m z hit resolution (inner layers, perp. tracks) SVT+DCH: (p. T)/p. T = 0. 13 % p. T + 0. 45 %, (z 0) = 65 m @ 1 Ge. V/c DIRC: K- separation 4. 2 @ 3. 0 Ge. V/c 3. 0 @ 4. 0 Ge. V/c EMC: E/E = 2. 3 % E-1/4 1. 9 % April 27, 2006 F. Forti - Super. B Strawman Detector 3

April 27, 2006 F. Forti - Super. B Strawman Detector 4

Machine backgrounds • In “traditional” Super BFactory designs – Luminosity obtained with large beam currents (among other things) • 4. 1/9. 4 A for Super. KEKB @ 4 x 1035 • 6. 8/15. 5 A for Super. PEP-II @ 7 x 1035 – Background a significant problem • In December Linear Super. B design – Small fraction of store beam extracted from damping ring at each collision. – Very low current at the IP make backgrounds negligible – Low collision frequency implies event pileup • In March Super. B design – Beam currents are moderate: 1. 5 A @ 1036 – Background important, but should not be a huge problem (smaller than in current BFactories) – Collision at every turn: no pileup, and continuous timestructure as in current BFactories. April 27, 2006 F. Forti - Super. B Strawman Detector 5

Types and level of backgrounds • Extrapolations from current machines – Full simulation is needed to completely understand backgrounds • Beam gas • Synchroton radiation • Both proportional to current – Should not be a problem at Super. B • They become a problem at higher currents • Luminosity sources (eg radiative Bhabhas) – Need careful IR design. – Angle crossing helps (see PEP-II/KEKPB comparison) April 27, 2006 F. Forti - Super. B Strawman Detector 6

BABAR Interaction Region Detector April 27, 2006 F. Forti - Super. B Strawman Detector 7

Radiative Bhabhas April 27, 2006 F. Forti - Super. B Strawman Detector 8

More sources of background • Beam-beam interactions – Potentially important, but probably under control in the low disruption regime. • Touschek background – Intra beam scattering. Goes like 1/E 2. Improves with smaller asymmetry. Increases with beam density. Need further study • Thermal outgassing – Due to HOM losses. Not an issue with small currents • Injection background – Needs further study with the 1 collision/turn scheme. • Bursts – Due to dust. No real cure. Need robustness of detector April 27, 2006 F. Forti - Super. B Strawman Detector 9

Background bottom line • Probably reasonable to assume machine background is not larger than what with have today at Babar and Belle. • Need to design a robust detector with enough segmentation and radiation hardness to withstand surprises (x 5 safety margin) – Seems within reach of current technology – There are critical points, though: • Inner detector radius likely to be reduced more background • Bhabha scattering at small angle can become an issue because of smaller boost more occupancy, more radiation damage • IR design is critical – Radiative Bhabhas – Syncrotron radiation shielding – Shielding from beam-beam blow up April 27, 2006 F. Forti - Super. B Strawman Detector 10

Beam Energy Asymmetry • Machine design prefers lower boost – – Damping rings more similar Babar: 9 + 3. 1 βγ=0. 56 Belle: 8 + 3. 5 βγ=0. 45 Super. B? : 7 + 4 βγ=0. 28 • Most obvious effect on detector – Larger solid angle coverage – Smaller decay vertices separation • We can afford to have a lower boost only if the vertexing resolution is good: – – small radius beam pipe very little material in b. p. and first layer Studies indicate a b. p. of 1 cm would be OK Need a realistic beam pipe design to confirm the viability of the lower boost. – How much cooling is needed in the beampipe ? • Symmetric running is also being studied – Could reduce boost-induced energy smearing in t mg analysis April 27, 2006 F. Forti - Super. B Strawman Detector 11

Beam Pipe Radius • Small beam pipe radius possible because of small beam size – Studied impact of boost on vertex separation (B pp) – Beampipe hypothesis (no cooling) • • 5 um Au shield to protect from soft photons 0. 5 cm 200 um Be and 5 um hit resolution (0. 21% X 0) 0. 5 cm 300 um Be and 10 um hit resolution (0. 24% X 0) 0. 5 cm 500 um Be and 10 um hit resolution (0. 29% X 0) – Rest of tracking is Babar Separation significance April 27, 2006 Proper time difference resolution F. Forti - Super. B Strawman Detector 12

Beam Pipe Thickness • With 1. 5 A beam currents the beam pipe will require cooling. – Beampipe design is being developed – Study effect of beampipe thickness • • Assume boost=0. 28 B pp decay 10 um hit resolution 1 cm beampipe should allow good performance even with bg=0. 28 April 27, 2006 Ba. Bar F. Forti - Super. B Strawman Detector Proper time difference resolution 13

Energy • Is it interesting to run at different energies ? – Υ(5 s): not an issue for the machine – oscillation of Bs rapid for TD analysis • Required resolution very hard to obtain • Still it might be possible to measure g through timeintegrated measurement branching fractions • Bs Df • Bs K+p+p 0 Renga/Pierini April 27, 2006 F. Forti - Super. B Strawman Detector 14

Energy II • Is it interesting to run at the tt threshold or at the y(3770) ? – Luminosity will be around 1035 – Still more than at tau-charm factories – Studies going to on on physics case • • Absolute D branching fractions, rare decays Form factors Unitarity tests with charm D mixing ? Use coherence of initial state • CP violation <Dz>/s(Dz) vs bg • Boosted operation – Is there something to be gained to run at low energy with boost ? – It might be possible to separate (a little bit) the D vertices April 27, 2006 F. Forti - Super. B Strawman Detector 15

Silicon Vertex Tracker • Vertexing – Two monolithic active pixel layers glued on beam pipe • Since active region is only ~10 um, silicon can be thinned down to ~50 um. x 5 scale with 10 mm radius • Good resolution O(5 um). BP, 6 mm pixel chip • Good aspect ratio for small radius (compared to strips) • Improves pattern recognition robustness and safety against background • needs R&D: feasability of MAPS, overlaps, cables, cooling • Quite a bit of R&D going on on MAPS April 27, 2006 F. Forti - Super. B Strawman Detector 16

MAPS R&D CAP chip (Belle collaborators) CAP 1: simple 3 -transistor cell TSMC 0. 35 mm Process Vdd Source follower buffering of collected charge Reset M 1 M 2 Restores potential to collection electrode Collection Electrode M 3 Row Bus Output Gnd Column Ctrl Logic Pixel size: 22. 5 mm x 22. 5 mm 1. 8 mm Column Select 132 col*48 row ~6 Kpixels CAPs sample tested: all detectors (>15) function. TESTED IN BEAM. April 27, 2006 F. Forti - Super. B Strawman Detector 17

MAPS R&D II • SLIM chip (Babar collabor. ) Charge sharing threshold 55 Fe ST 0. 13 um triple well technology Single pixels tested with source Full signal processing chain PRE SHAPER DISC X-rays Noise only (no source) LATCH threshold April 27, 2006 =105 m. V =12 m. V F. Forti - Super. B Strawman Detector Landau peak 80 m. V 12501640 90 Sr electrons saturation due to low energy particle. 2200 3000 (e-) 18

Silicon Vertex Tracker • Intermediate silicon tracking – More or less like the current Si strip detectors: • 5 layers of 300 um Si, strip lengths 5 -20 cm, pitch 50 -200 um, shaping time 100 -400 ns – Reduction in thickness would be desirable, but not essential • Possibility of 200 um Si in inner layers – Small angle region will require special attention due to the high Bhabha rate 20 cm 30 cm April 27, 2006 40 cm F. Forti - Super. B Strawman Detector 19

Central Tracker Normal cell(17. 3 mm) • Babar and Belle Drift Chambers – – Both use He based gas mixture Cell size 12 -18 mm Maximum drift time ~500 ns Resolution in the best part of the cell ~100µm – Expect that either OK. • Solid state tracking – an all-silicon solution evaluated, but not performant at low momentum, expensive, and not really needed with moderate backgrounds Small cell(5. 4 mm) • Need to optimize cell size against occupancy – Belle has developed a fast gas small cell DCH, but with a degraded resolutions (5. 4 mm, ~150µm) • Solutions exists, although a full design is needed April 27, 2006 F. Forti - Super. B Strawman Detector 20

Particle Identification • Current solutions for K identification – Low p: • d. E/dx (both Babar and Belle) • TOF (Belle only) – High p: dedicated Cherenkov detector • DIRC (Babar) – ring imaging cherenkov counter • ACC(Belle) – aerogel threshold cherenkov counter – Coverage: • only barrel(Babar) • barrel+endcap (Belle) • Evolution – Ring imaging is superior to threshold counters • Need to resolve background and mechanical issues – Forward and backward endcap coverage very desirable to increase effective luminosity • A different kind of problem • R&D is needed April 27, 2006 F. Forti - Super. B Strawman Detector 21

Babar PID • Stand-off box, filled with water expands cone on PM – Source of backgrund • Barrel-only device • Mechanical interference in the backward direction April 27, 2006 F. Forti - Super. B Strawman Detector 22

Belle PID • Aerogel Cherenkov Counters, Time of Flight – No high mom. PID for endcap – Material (ACC+TOF ~ 0. 35 X 0) April 27, 2006 F. Forti - Super. B Strawman Detector 23

Evolution: Babar-Style Fast DIRC • Replace SOB with compact readout • Tested in beam with – Hamamatsu Multi Anode Photo Multipliers – Burle Micro Channel Plate PMTs April 27, 2006 F. Forti - Super. B Strawman Detector 24

DIRC with timing: TOP Simulation 2 Ge. V/c, q=90 deg. • Cherenkov ring imaging with precise time measurement – Quartz radiator (2 cm-thick) • Basic study was already done. – Photon detector (MCP-PMT) • Good time resolution < ~40 ps • Single photon sensitive under 1. 5 T – Test with Ga. As. P photo-catode + MCPPMT very promising -K separation power April 27, 2006 F. Forti - Super. B Strawman Detector K d-ray, had. int. 25

Focusing Aerogel-RICH • New imaging technique by introducing multiple radiators n 1<n 2 n 1>n 2 n 1 n 2 Focusing type n 1 n 2 n 3 n 4 n 1<n 2<n 3<n 4 Defocusing type n 1 n 2 n 3 n 4 n 2<n 1<n 4<n 3 Increase Cherenkov photons without loosingle angle resolution due to emission point uncertainty April 27, 2006 Take full advantage of controllable index of aerogel F. Forti - Super. B Strawman Detector 26

Electromagnetic calorimeter • Both Babar and Belle use Cs. I(Tl) calorimeters are suitable for Super. B – signal decay time of ~. 75µs (dominant) and ~3µs are OK • Cs. I(Tl) is too slow for endcap – need to deal with Bhabha rate spatial and temporal overlaps. – especially if possible to extend coverage to 100 mrad, beam line elements allowing. • Babar forward is 350 mrad, Belle forward 200 mrad, backward 400 mrad • Encap replacement is needed – In the case of Babar, a backward endcap needs to be added altogether • Solutions seem to be viable with some R&D April 27, 2006 F. Forti - Super. B Strawman Detector 27

Candidate materials • Pure Cs. I – Fast (16 ns) – Low light yield (2500 g/Me. V) • LSO or LYSO – High light yield (27000 g/Me. V) – Speed OK (47 ns) – Expensive April 27, 2006 F. Forti - Super. B Strawman Detector 28

Other Detector components • Muon and KL detector – Inside the return yoke of magnet – It doesn’t seem to be a problem – avalanche mode RPC, LST, scintillator are all viable • Trigger/DAQ – Not substantially different from current schemes. – Keep open trigger scheme – Need to try vetoing Bhabhas at level 1 – Data rate seems well manageable April 27, 2006 F. Forti - Super. B Strawman Detector 29

Reusability of Babar and Belle • Large (expensive) portions of Babar or Belle would be reusable – Barrel calorimeter – Magnet – Barrel LSTs for Babar • But large subsystems need to be replaced or significantly upgraded – – Tracking and vertexing Particle ID Endcap calorimeter Trigger/DAQ • Babar or Belle seem good foundations for a Super. B detector – But need to look in detail at integration and mechanical structure issues April 27, 2006 F. Forti - Super. B Strawman Detector 30

From Hitlin’s talk at March 06 LNF April 27, 2006 F. Forti - Super. B Strawman Detector 31

From Hitlin’s talk at March 06 LNF April 27, 2006 F. Forti - Super. B Strawman Detector 32

Outlook • A detector for Super. B seems to be feasible • An R&D plan needs to be formulated to address the remaining issues – Vertexing – Particle ID – Calorimetry • Babar and Belle provide excellent foundations for a detector at Super. B • More detailed studies will be possible once the machine parameters have settled. April 27, 2006 F. Forti - Super. B Strawman Detector 33