Guy Wormser, Super B-Factory Workshop, Jan 04 1 BELLE/BABAR present background situation zThe...

Guy Wormser, Super B-Factory Workshop, Jan 04

1

BELLE/BABAR present background situation

The information from BELLE:http://www.phys.hawaii.edu/~superb04/slides.htmlMost important talks:

Summary from Haba-san, Current Belle background from Tajima-

sanAlso some informal inputs

http://www.phys.hawaii.edu/~superb04/slides.html

http://www.phys.hawaii.edu/~superb04/slides.html


2

BELLE Background general featuresCoasting backgrounds

Overall smaller background level « SVT » background perfectly described by the

sum of SR, beam gas and Touschek Strong Touschek effect seen in the DCH TOF (+50%) and Muon (x5) see larger bkg in

collision than sum of single beams Injection backgrounds: not a problem !Burst events: Happen one every few hours,

last ~1 sec, spontaneously digestedTrips: a few per day


3

SVD Upgrade in 2003 summer

rbp = 2.0 cm 3 layers Rad. hardness

rbp = 1.5 cm 　　 4 layers 　　 > 10 MRad (DSSD) 　　 > 20 MRad (readout chip)

~ 1 MRad

Better vertex resolution / tracking efficiency


4

Other sub-detectors

No large difference for BG (current diff. causes small diff. ?)

No problem

SVD 1.6(Jun, 2003)

SVD 2.0 (Dec, 2003)

beampipe radius

2.0 cm 1.5 cm

HER/LER 1.0 / 1.5 A 1.1 / 1.6 A

CDC leak current

19 A 21 A

TOF rate 20 kHz 25 kHz

EFC rate 2.1 kHz 2.2 kHz


5

10% occupancy means

10k ch has unnecessary

hits!


6

Extraction SR in HER Single Beam

50 mA 100 mA 200 mA

400 mA 600 mA 800 mA

HERParticle

SR

Hard-SR simulation

Cool work!

O. Tajima


7

translated differently as Unbelievable ! (Karim)I don’t believe it (Steve, O)


8

Study of Touschek EffectTouschek contribution < 20 % at collision ~ 50 % at single beam 31 % in simulation

Smaller beam-size (larger density)

larger background

If no Touschek

Touschek contributionmust be corrected

Collision run

Single beam run

O. Tajima

What we learn here is

beam is different for

collision.


9

Towards a quantitative comparison

Some numbers available but direct detailed quantitative comparison with BABAR is not yet possible!!

BELLE figures of merit Integrated dose in Calorimeter 100 Rad Dose rate in SVT layer1, not very much phi dependant 100

krad Integrated dose in all their SVTs 1M Rad Current drawn from their chamber 1 mA

Seems certainly more confortable than here but by how much?How to compare:

BELLE_SVT first layer: Occupancy 10% but long shaping time (800ns)Dose: remove injection, radius different, different lengths,…DCH different volume, gas gainEMC remove injection, check theta dependencies,etc…


10

Comparison templates (1)

System SVT Layer 1 Sensor used: Occupancy Strip width, lenght, radius, integrating time Parametrization as fct of HER (2nd degree polynomial),

LER (idem) for single beams Plot of [observed – sum singles] vs lumi Integrated dose as function of integrated lumi for running integrated dose during injection Ratio of max/min as function of Phi Average Trip rate per day from the SVT protection system Bias On/off during injection?


11

Comparison template (2)

System DCH Sensor : Total current draw Gain, volume, min-max radius,length Parametrisation as function of single beams

(second order poly) Plot of (observed –sum of single beams) as

function of lumi Integrated dose per wire in C/cm Average spikes due to dust event per day;

average trip per day Signal any strong azimutal of z dependance


12

Touschek effect at PEP-II


13

Sensor BLLC2081 as fct of HER and LER


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Beam and beam and Touschek

Sensor HER LER Lumi BB Touschek

PR04 2081 0 Q-4500 0 0 2000

PR04 3011 0 Q-800 600 0 0

3020 Q-200 0 4500 0 0

3030 Q-30 Q-25 500 50 0

3042 0 Q-700 0 1000 0

3072 0 Q6000 0 2000 1000

3101 L-20 Q-100 1000 50 0

3132 L-40 L-10 1200 0 0

3142 0 Q-1200 0 1000 0

3172 L7 L30 600 0 0

4042 L-7 L-30 600 0 0

4072

4112 0 X-140 0 500 0

7017 Q-200 L-30 0 0 0

7044 L25 0 20 0

7052 Q10 X250 4000 0 0

8012 Q200 0 4000 0 0

PR12 8072 L3000 0 0 25000 0


15

BLSC 3072


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3072 vs HER


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Comparison template (3)

System EMC Sensor : Number of clusters above 1 MeV (or

mean energy per cluster?) Radius, crystal size, shaping time, amount of X0

in front Single beam parametrization (second order

polynomials) for Her and LER Observed –(sum of singles) as function of Lumi Integrated dose Maps as function of Tetha; as

function of integrated lumi Any azimutal effect?


18

Extrapolations for SUPERKEK and Super PEP

THe IR design is key to the background level The consensus IP looks like the present KEKB but with more

magnetic field and closer to detector: the sensitivity to rad Bhabbas will increase compared to present KEK

SuperK rule of thumb: x20 all present background Not so conservative in my mind because the present KEKB

background is well described by just the sum of SR, BeamGas and Touschek but I have strong doubts this will be the complete list at 10**35

On teh other hand, it makes no sense to extrapolate present PEP-II numbers x100 since the Super IR should be more background friendly than the present one.


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Conclusions

KEKB background situation is certainly better than ours. This is due to the absence of sweeping fields very close to the IP

A detailed comparison is not yet possible but is very desirable. I would like an agreement/comments on the proposed templates, and send them to KEK while we fill them

KEKB is able to describe their inner background by a sum of only three terms: SR, Beam Gas and Touschek

We need to make an effort to quantify our SR and Touschek contributions.

The neutron rate outside of the detector is another critical element

(they have a very large collision term in the muon system, although the overall rate is low)

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Guy Wormser, Super B-Factory Workshop, Jan 04 1 BELLE/BABAR present background situation zThe...

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