Документ взят из кэша поисковой машины. Адрес оригинального документа : http://zebu.uoregon.edu/~uochep/talks/talks05/lumi.pdf Дата изменения: Thu Sep 1 20:15:35 2005 Дата индексирования: Tue Oct 2 09:56:28 2012 Кодировка:

Discussion items for luminosity measurements at the ILC
David Strom ­ University of Oregon

· My suggestions are based on my exp erience with the LEP I OPAL luminosity measurement: This was an enormous effort based on work of scores of p eople b etween (1990 conception) to 2000 (final publication)

Eur. Phys. J., C14 (2000)373-425 Most recent result (measurement of QE D ) running just accepted for publication

CERN-EP-2005-024
Snowmass 05

1

23 August 05 ­ David Strom ­ UO


· Imp ossible to measure luminosity 1 3 distribution without small radial bias and very go o d resolution Best to measure p osition of the electromagnetic shower rather than electron track

Since the radial measurement must b e very well understo o d arrange other cuts to remove only a few events

Snowmass 05

2

23 August 05 ­ David Strom ­ UO


· Example electromagnetic sp ectrum with and without acollinearity cut
OPAL
Prob./0.01 10 Prob./0.01
-1 a) -1 b)

10

10

-2

10

-2

10

-3

10

-3

10

-4

10

-4

10

-5

10

-5

10

-6

0.4

0.6

0.8

1

1.2 1.4 ER/Ebeam

10

-6

0.4

0.6

0.8

1

1.2 1.4 EL/Ebeam

Snowmass 05

3

23 August 05 ­ David Strom ­ UO


· Use very tight acollinearity cut for energy tune-up
OPAL
Prob. / 0.01 1 10 10 10 10 10 10
-1 -2 -3 -4 -5 -6

0

0.2

0.4

0.6

0.8 1 1.2 ER / Ebeam 8.75 < R < 11.75

Prob. / 0.01

1 10 10 10 10 10 10
-1 -2 -3 -4 -5 -6

0

0.2

0.4

0.6

0.8

1 1.2 EL / Ebeam 8.75 < R < 11.75

Snowmass 05

4

23 August 05 ­ David Strom ­ UO


· Make detector uniform so that no fiducial cuts in etc will b e needed. · What will the background from off-momentum b eam particles b e? Dep ends on vacuum near the interaction region. Don't make the pads to o big in either radius or phi, need to separate background clusters from real Bhabhas. · Background from low momentum pairs will probably b e more imp ortant Detector must b e able to measure "min-bias" shap e of background on a bunch-by-bunch basis

Snowmass 05

5

23 August 05 ­ David Strom ­ UO


Detector Geometry · It is essential to survey the detector at the micron level with cosmic ray muons or test b eam. Electronics must have MIP sensitivity even if it is not needed by the luminosity measurement MIP sensitivity needed for p ossible muon veto (See Graham Wilson's Calorimeter talk). · Detectors should fit on a single wafer
8 inch wafer

· SiD geometry Rmin 8.7 cm ( 50mrad) Rmax 24.7 cm( 150mrad) 8 inch wafers would b e needed

64 radial pads

Moliere Radius

· Rate at 500 GeV is 8 bhabhas bunch train ­ Inner radius could b e much larger and 6 inch wafers used
Snowmass 05

6

23 August 05 ­ David Strom ­ UO


Is this segmentation reasonable? · Assume 20 layers, 1 X0 and 2 X0 · Assume two readout chips/wafer (128 channels/chip) 2 в 16 в 20 в 2 = 1280 electronics chips · Assume Successive Approximation ADC with 12 bits + range, digitizing at 3MHz (internal clo ck is 36MHz). Data rate is 576 MBytes/s/chip during bunch train ( 3.0MBytes/s sustained) · On b oard electronics cost will b e dominated by development costs (very similar to run needed for test b eam) · Won't save much money by reducing channels/wafer · Power consumption should b e reasonable, but no design yet for co oling in the endcap in SiD. LDC will b e easier.
Snowmass 05

7

23 August 05 ­ David Strom ­ UO


· Biggest unsolved problem: How to avoid gaps in end cap/lum cal coverage

· Go o d but imp ossible to op en

· Has dead area b etween LAT and endcap

Snowmass 05

8

23 August 05 ­ David Strom ­ UO