Machine Detector Interface Summary Junji Haba, KEK

Beam background Another very important issue in a high luminosity machine other than L. Where it comes?.

What is beam background?

10% occupancy means 10k ch has unnecessary hits!

Types of Accelerator Backgrounds Synchrotron Radiation (SR) Lost beam particles (BGB) Touschek scattering Luminosity backgrounds M. Sullivan Nice introduction for non machine physicist.

Lifetime Effects Quantum lifetime –(Not a problem as the RF voltage is high.) Residual gas –Bremsstrahlung –Elastic scattering –Small change as the gas is only a few times worse. Touschek effect Luminosity –Bhabha (e+e-  e+e-) –Radiative Bhabha (e+e-  e+e-  ) Beam-beam tune shift J. Seeman Different view from Machine operation

Synchrotron radiation from up/down stream Off momentum/orbit beam particle

Study of Touschek Effect Touschek contribution < 20 % at collision ~ 50 % at single beam 31 % in simulation Smaller beam-size (larger density)  larger background If no Touschek Touschek contribution must be corrected Collision run Single beam run O. Tajima What we learn here is beam is different for collision.

Touschek lifetime versus RF voltage Quantum lifetime Smaller bunches J. Seeman

Luminosity backgrounds  Radiative Bhabhas These are initial state radiation events. In single ring colliders, these events were buried in the beam envelope and were eventually lost when the beam went through a bending magnet, many meters from the detector. The 2 ring B-factories, with shared quadrupoles and bending magnets closer to the IP, these events come out of the beam envelope much sooner and can be a source of detector background.  Touschek scattering at the IP? Touschek scattering ~1/  x  y. For PEP-II, given the Touschek lifetime to be about 400 min and the average beta x, y around the ring is ~30 m and that the IP betas are 0.3 and we find a Touschek scattering enhancement at the IP of Normalized by length (1cm vs 2200 m) we get the IP rate to be ~7e-3 of the ring. For a 2A beam then there are ~1  10 7 Touschek events per second at the IP from the LER. This is a very crude calculation and we need to check this guess with a full blown simulation. M. Sullivan Seem very serious for PEPII as Luminosity grows up!!

M. Sullivan

Background parametrization based on February 2002 data The observed background is roughly twice larger than the sum of the single beam contributions G. Wormser Clean example from BaBar

SVT Background from HER (BW:MID) Moves toward half-integer HER sensitive SVT module (Does not have threshold shift problem): Background almost doubled after move to half-integer Again it has come down a bit during run-4 Note peak occupancy is 150% higher than average occupancy! For occupancies in all SVT modules, see: Another type of background, not on luminosity nor on beam current Degradation of the detector itself G. Wormser

It was noted that it may be difficult to distinguish “beam-beam” effect from “luminosity” background. KEKB experience: “beam-beam” effect make HER beam size larger and hit the smallest acceptance of the ring resulting increase of background.

What is wrong with the background? 1)Degradation of the detector itself. Light yield of scintillation crystal Gain drop of DC wire Damage in the readout electronic 2)High occupancy degrades the event reconstruction also. 3)Very high data trasfer rate

H. Kelsey Gain drop in DCH (BaBar) Still can survive for while by rasing HV

M. Kocian Light yield reduction in CsI (BaBar) as long as 10^34 operation

cf Belle ECL By A. Kuzumin Also in Belle 1/10 though.

Limits were set to the HER magnets. Synchrotron radiation from HER upstream magnets. This killed SVD 1.0 The downstream chamber was replaced with a Cu chamber SVD 1.1 SVD1.4 25% gain drop in 1.5 years SVD1.1 60% gain drop in 5 days SVD 1.4 S. Stanic Gain drop in Belle SVD

Resolution degration with occupancy G. Wormser Current operation Why we have very smallest beam pipe with very high background????

Example in G. Wormser Reconstruction efficiency of D* is really degraded seriously under high background

Decrease of x20 occupancy The electronics(Shaper/QT) deadtime is clouding out proper track hits under the high occupancy. Thus tracking efficiency and resolution depend on the readout system. Deadtime = 2200ns Deadtime = 600ns More proper hits to reconstruct a track! Senyo

Larger dead time. Greater loss of luminosity!

Do we understand the current beam background? G. Wormser from BaBar O. Tajima from Belle S. Stanic form Belle

Monitoring system for SVD2 kRad range RadFET RTD temp. sensor Low Gain PIN for Beam Abort Interlock High Gain PIN for monitoring/logging The conceptual design remained the same as for SVD1.4, however, we changed many things: New types of “monitoring hybrids”, specially designed for SVD2.0 IR 2 nd and 3 rd layer RadFET/Pt100 hybrids 1 st layer RadFET/PIN/Pt100 hybrids S. Stanic Monitor tool is very important!

Conclusions for short term issues We have to look far ahead: Minimum 3 years Look for worst case scenarios! Look for end-product effects! BABAR issues –Immediate concerns: SVT ATOM chip, IFRForward endcap –Next on-line: DCH DAQ –Longer term issues: SVT and EMC in 2008 Changes in background issues –Beam-beam tails –injections –trapped events

Conclusions for short term issues We have to look far ahead: Minimum 3 years Look for worst case scenarios! Look for end-product effects! BABAR issues –Immediate concerns: SVT ATOM chip, IFRForward endcap –Next on-line: DCH DAQ –Longer term issues: SVT and EMC in 2008 Changes in background issues –Beam-beam tails –injections –trapped events

Extraction SR in HER Single Beam 50 mA 100 mA 200 mA 400 mA600 mA800 mA HER Particle SR Hard-SR simulation Cool work! O. Tajima

Simulation gives an extremely good expectation! translated differently as Unbelievable ! (Karim) I don’t believe it (Steve, O)

Radiation Dose at SVD 1 st layer At Maximum Currents: HER 1.1A, LER 1.6A Outer-direction ~ 0 degree Inner-direction ~ 180 degree Particle-BG (LER) 22 (18) kRad/yr 14 (11) kRad/yr Particle-BG (HER) 44 (53) kRad/yr 29 (33) kRad/yr SR-BG 17 (8) kRad/yr 33 (29) kRad/yr Total 83 (79) kRad/yr 76 (73) kRad/yr (…) is 1nTorr pressure Data and simulation is consistent Touschek contribution is reduced based on measurement We can trust simulations Its uncertainty for abs. may be factor a few O. Tajima Simulation gives an extremely good expecttion! which can be translated as Unbelievable ! (Karim) I don’t believe it (Steve, O)

What background expected for the superBfactory? Good understanding of current background is being establisehd. Serious simulation study just started. Very high background extrapolated from the current experience (BaBar). Degradation may be manageable(BELLE).

K. Trabersi Serious study Just started with reallistic lattice

K. Trabersi 10 times higher. Smaller than they assumed in the detector design. 100 kRad/yr 1 MRad/yr

K. Trabersi Slight modification of Q magnet position easily changes the dose!

Very simple extrapolation. Is it OK to design the next detector beased on it?

About 80% of efficiency is kept in the slow  efficiency under x20 occupancy. Need higher efficiency to keep full reconstruction eff. Slow  efficiency from B  D*(D  slow )  recon. eff. of the slow pion ~ single track efficiency of slow p B  D*  reconstruction eff. including geometrical acceptance Senyo

Vertex resolution w/ B  J/  K S Vertex resolution is kept less than 160  m  (Z CP -Z tag ) Senyo

M. Kocian

PEPIII may be very similar to KEKB, that is simple extrapolation has no meaning!!

Idea for Hard-SR reduction HER-beam If we can bend beam  photon-stop far place SR If 2 times far place  1/4 BG Possible headache for KEKB- type IR design. O. Tajima

Injection Continuous Injection (trickle ) is necessary to keep the peak luminosity. To maximize the efficiency, switching injection pulse by pulse (LER HER) is very interesting.

Lifetime for luminosity Lifetime contribution HER lifetime (min) LER lifetime (min) Quantum Vacuum Touschek36045 Luminosity2550 Beam-beam tune shift 20 Total life w/o b-b2120 Total life with all10 J. Seeman We can’t live without a continuous injection anyway.

Beam pipe issue (today) Can we have smaller beam pipe ? Sullivan, – SR, I^2R, and HOM ?? Many technical obstacles…. Katayama –Beam is flat. Why not flat beam pipe? –What we can get with extremely flat beam pipe.

Side view of S-F beam pipe Ｖａｃｕｕｍ or accelerator components (nano beta??) Ｓｉｌｉｃｏｎ ｖｅｒｔｅｘ ｄｅｔｅｃｔｏｒ （３００  m thick) Beryllium beam pipe (500  m) 1.6 cm N. Katayama

S-F geometry vs current geom. Error on flight distance (  m) See difference in scale N. Katayama Perfect reconst. Bs mixing, B  D  etc

Summary of summary Many studies just started with the 0 th version of IR design It’s too simple-minded to design the detector based on the straight extrapolation from now. Hope to discuss in the next WS also on mechanical interface btw detector and machine like support, heat treatment around beam pipe, concept of IR assembly….