R. Messner
Sept 23, 2003
9/22/03 R. Messner 2
• Inner Barrel – luminosity related
• Backward endcap – luminosity related
• Inner portion of forward endcap - luminosity
related; a small amount (5%) due to the HER
• Outer portion of forward endcap – dominated by
LER beam scraping on beamline elements;
possibly still have some albedo from HER dump
(outermost gap only)
9/22/03 R. Messner 3
Babar Elevation View
• The LER beam approaches the forward endcaps from the south tunnel; the HER beam is exiting through the forward endcaps toward the south
9/22/03 R. Messner 4
Forward Endcap after Summer 2002
9/22/03 R. Messner 5
• Limits set by electronics:
– strip signal held in FEC for 12.5 µs (dead time)
⇒ max rate = 80 kHz/strip (~30 Hz/cm2).
• Limits set by the streamer mechanism:
– Very dependent on the local properties of RPC materials and the operating point: this is presumably somewhat lower than the
electronics limit.
• RPC damage:
– Degradation is also likely to start at similar values.
• Reconstruction:
9/22/03 R. Messner 6
• Singles rates for barrel RPCs show a linear dependence with the
luminosity.
• The slope of the fitted straight line is higher for layers closer to the beam pipe; it gets essentially flat for outer layers, except for layer 18, where
positive slopes are seen again.
Sextant 0, Layer 1
Sextant 1, Layer 10
Sextant 5, Layer 18
9/22/03 R. Messner 7
Counting rates in the forward endcaps
0 1 106 2 106 3 106 4 106 5 106
L a y er 15 L a yer 14 L a y er 12 L a yer 11 L a ye r 10 Lay er 9 Lay e r 8 La y e r 7 Lay er 6 La y e r 5 Lay er 4 Lay e r 3 Lay er 2 Lay e r 1 Layer_Rates_from_May13_15_Runs Laye r Sca ler Rat e (H z) Layer Number
Outer Layer rates follow LER beam losses
9/22/03 R. Messner 8
Inner forward endcap
These are the closest to the IP
Expect them to be the most sensitive to the luminosity Small dependence on the HER current
9/22/03 R. Messner 9
1-22-2002 Data: Inner layer modules vs. PEP luminosity
0
5 104
1 105
1.5 105
2 105
0 500 1000 1500 2000 2500 3000 3500 4000
Special ’coast’ run 1-22-2002 Layer 10 Sums
Layer 7 Sums
Layer 4 Sums
Layer 1 Sums
S u m o f Lay e r S c al a rs ( H z ) PEPLUM
9/22/03 R. Messner 10 0 500 1000 1500 2000 2500 3000 3500 4000
-200 0 200 400 600 800 1000
ifrscalars_tableout_l8-l1_2-10_0800_2300 SREC8W9 SREC7E11 SREC6W5 SREC5W5 SREC4W1 SREC3W1 SREC2E1 SREC1E5
y = 1205.2 + 0.67905x R= 0.95414
y = 1473.2 + 0.80513x R= 0.90083
y = 2699.2 + 0.9823x R= 0.80917
SRE C 8 W 9 HERCUR
Zero LER current
9/22/03 R. Messner 11
X-Y hit distribution for the inner layers of the
endcap chambers (E. Robutti, May 2002)
• Hits in the inner layers of the endcaps are largely accumulated closest to
the beam pipe. Maximum values are now around 1.5 - 2 kHz/strip, or ~5
Hz/cm2.
9/22/03 R. Messner 12
Outer forward endcap
The first issue is to identify the sources.
The standard approach of correlating the background with
the luminosity or the beam currents doesn’t work.
9/22/03 R. Messner 13
The scaler rates do not necessarily follow the luminosity or currents
0 1000 2000 3000 4000 5000
0 100 200 300 400 500 600
HERCUR LERCUR PEPLUM HER CUR Time_Interval 0 5 104 1 105 1.5 105 2 105 2.5 105 3 105 3.5 105 4 105
0 100 200 300 400 500 600
SREC14E5 S R EC 1 4 E5 Time_Interval
9/22/03 R. Messner 14
The scaler rates do follow the time structure of the loss monitors We can fit the scaler rates to a linear function of the loss monitors
Time_Interval 0
5 104 1 105 1.5 105 2 105 2.5 105
0 100 200 300 400 500 600
Combined_Runs_Mar_28_30_with_fits blsc3072 blsc3042 bl sc3 072 Time_Interval 0 5 104 1 105 1.5 105 2 105 2.5 105 3 105 3.5 105 4 105
0 100 200 300 400 500 600
Combined_Runs_Mar_28_30_with_fits SREC14E5 14E5=3035.+blsc3042*8.34235+bls SRE C14E 5 Time_Interval
9/22/03 R. Messner 15
In fact, one can extrapolate a fit from one time period over a much wider range of losses
0 5000 1 104 1.5 104 2 104 2.5 104 3 104
0 2 104 4 104 6 104 8 104 1 105
Combined_Runs_Mar_28_30_with_fits
blsc3042
bls
c
30
42
blsc3072
9/22/03 R. Messner 16
Fits obtained from different sets of data compare well with a single data set – this can span a reasonably long period of time – so you have some predictive power
0 5 104 1 105 1.5 105 2 105
0 50 100 150 200 250 300
14W1= 11900.9+c1* 8.11852+c0*0.341792 (Jan6 fit) 13W1=11281+c1*10.4248+c0*0.6323 (Mar4 fit)
14W1=2779.87+c1*12.9558+c0*0.589909 (Mar 28 fit)
14W1= 12376.6+c1* 9.88297+c0*0.278536 (Apr13 fit)
SREC14W1
Scaler Ra
te
(
H
z)
9/22/03 R. Messner 17
How do we extrapolate to the future?
• Start with the given values of beam currents and luminosity
• The background run of 2-10-2002 and our experience during normal runs give us the dependence of the barrel and the inner forward endcap rates upon the beam currents and luminosity
• The replacement of the entire forward endcap in the summer of 2002 included the installation of a one inch iron plate providing shielding from the HER; we will neglect any remaining HER dependence
• Experience during normal runs provides the typical correlations
between the rates in the outer forward endcaps and the LER beam loss monitors
• We need a recipe to ‘predict’ the beam losses – this is necessarily a kludge, because common sense (and experience) says the details of the moment determine the nature of the beam losses
• For simplicity we choose the ansatz that the losses are proportional to the current
9/22/03 R. Messner 18
‘Predicting’ the behavior of the LER beam losses:
a)
Assume that the losses are
proportional to the current
b)
Use this and the fits to calculate a
rate for the outermost three gaps of the endcap
0 5000
1 104
1.5 104
2 104
2.5 104
3 104
0 500 1000 1500 2000
May_13_to_15_data_Layer_15_on blsc3072 blsc3042 Lo ss M onit o r C o u n ts ( a rb it ra ry sc al e) LERCUR (ma)
9/22/03 R. Messner 19
IFR: Projected Hit Rates
0 20 40 60 80 100 120
Oct/1/03 Oct/1/04 Oct/1/05 Oct/1/06 Oct/1/07 Oct/1/08 Oct/1/09
PEP_II_Projections_Sept_15_03_thru_2009
Layer 15 West/cm**2 Layer 15 East/cm**2 Layer 14/cm**2 Layer 12/cm**2
Layer 1/cm**2
Barrel Layer 1/cm**2
Laye r Ra te ( H z/ cm ** 2) Date
9/22/03 R. Messner 20
9/22/03 R. Messner 21
9/22/03 R. Messner 22
Summary
• The inner layers of the endcaps are probably going to run into problems in the region closest to the beam pipe. This is primarily a physics effect.
• The barrel looks like it will be fine in terms of rates.
• The outer modules of the forward endcaps suffer seriously from beam (mainly LER) background. Better shielding is necessary in order to attain their full functionality. Any extrapolation transforms a bad situation into an impossible one.
– The sources are strongly associated with the beam losses seen in the monitors looking at the 24m and 12m LER collimators.
– Have seen (temporary) evidence for other sources as well. – What can be done?
• Monitor the outer chambers • Tune to reduce the beam losses • Shielding
9/22/03 R. Messner 24
Search for background penetrating from layer 15 to layer 14
Hope: if found, will it point back to a source?
Can check to see if we are doing the right thing by looking for muons from the IP
Look for hits in two layers correlated in x
See where the pairs project to along the beamline
9/22/03 R. Messner 25
Layers 14 and 15 - distribution of the difference in x between hits in layer 14 and layer 15 (a hit in each layer is needed)
9/22/03 R. Messner 26
Layers 14 and 15 - The difference in x divided by the average x position This will be a constant for a specific source
9/22/03 R. Messner 27
Layers 14 and 15 - scatter plot of the difference in x between hits in layer and the x position
9/22/03 R. Messner 28
Layers 10 and 11 - distribution of the difference in x between hits in layer 10 and layer 11 (a hit in each layer is needed)
9/22/03 R. Messner 29
Layers 10 and 11 - The difference in x divided by the average x position Peak again corresponds to the muons coming from the IP
9/22/03 R. Messner 30
Conclude
• Method works well enough to identify the muons coming
from the IP
• Some evidence for a source located ‘far away’
• However, the resolution of the chambers is not sufficient to
pick out specific sources at the distances, e.g.,
corresponding to the downstream collimator, with this
method
• Only sensitive to higher energy, shower producing
background
9/22/03 R. Messner 31
9/22/03 R. Messner 32
Jerry’s loss monitors around blsc3042 versus time
-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4
0 200 400 600 800 1000 1200
ifrtable_l16-l9.2003.05-13.2148.05-15.1100 2:10:17 PM 6/24/03
VSSM26 VSSM27 VSSM28 VSSM29 VSSM30 VSSM31 VSS M 2 7 Time_Interval
9/22/03 R. Messner 33
Jerry’s loss monitors in the
region around the downstream collimator versus blsc3042
-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4
0 5000 1 104 1.5 104
ifrtable_l16-l9.2003.05-13.2148.05-15.1100 2:12:51 PM 6/24/03
VSSM26 VSSM27 VSSM28 VSSM29 VSSM30 VSSM31 VS S M 27 blsc3042
9/22/03 R. Messner 34
The use of Jerry’s loss monitors can improve the comparison between the fit and the observed rate in layer 15
0 1 105 2 105 3 105 4 105 5 105 6 105 7 105 8 105
0 1 105 2 105 3 105 4 105 5 105 6 105 7 105 8 105 May_13_to_15_data_Layer_15_on
15E7 fit with a constant and the two collimator loss monitors 15E7 fit with VSAM30 and the two loss monitors
15E 7 r a tes pr ed ic ted fr om f it ( H z ) SREC15E7
9/22/03 R. Messner 35
Note, however: Jerry’s loss monitors are not always activated For example, here VSAM30 (red) sees very little relative to VSAM29
-1 0 1 2 3 4 5
0 100 200 300 400 500 600
Combined_Runs_Mar_28_30 VSSM30 VSSM29 Loss M oni to r R ead in g (a rb it ra ry sca le ) Time Interval
9/22/03 R. Messner 36
Neutrons?
• Belle says their background rate is due to neutrons
• Determined by matching monte carlo predicted
attenuation with observed rates
9/22/03 R. Messner 37
Layout of Belle Forward Endcap
9/22/03 R. Messner 38
LER Background Rates in Belle
9/22/03 R. Messner 39
Plot our data with Belle’s, converting our iron into an equivalent number of Belle layers and accounting for extra shielding in front of Belle’s
chambers
The slopes are quite different – argues against a large contribution from neutrons 1000 104 105 106 107
0 5 10 15 20
Belle Rate (Convert Hz/cm**2 to Hz using Babar conversion)
Babar Layer Sums - LER only run
Babar Layer Sums - normal run
y = 1.4892e+06 * e^(-0.26756x) R= 0.9978
y = 1.5623e+07 * e^(-1.5238x) R= 0.99862
y = 2.7877e+06 * e^(-0.70475x) R= 0.99976
Ra te p e r l a y e r in H z
9/22/03 R. Messner 40
9/22/03 R. Messner 41 0 1000 2000 3000 4000 5000
0 500 1000 1500 2000
ifrscalars_tableout_l8-l1_2-10_0800_2300 11:10:41 AM 10/7/02
SREC8W9 SREC7E11 SREC6W5 SREC5W5 SREC4W11 SREC3W11 SREC2E1 SREC1E5 Modul e Sc al ar R a te (H z) LERCUR Zero Her current
9/22/03 R. Messner 42
2-10-2002 Data: L18-11 modules vs. HER
One inch Fe shield installed in summer 2002
0 1 104 2 104 3 104 4 104 5 104 6 104
-200 0 200 400 600 800 1000
background_run_02-10_0800_2300 SREC18W3 SREC17E3 SREC16E3 SREC15E1 SREC14W7 SREC13W7 SREC12W5 SREC11E11
y = 4128.5 + 47.27x R= 0.99687
SR
EC18
W
3
HERCUR Zero LER current
9/22/03 R. Messner 43
Are we still affected by the HER albedo? Look at an old background run • Best determined by doing a HER-only run
• For now, look at outer layer rates versus the LER loss monitors
• Last year the HER contribution could get very large (the standard was about half of the layer 18 counting rate):
2 105 4 105 6 105 8 105 1 106 1.2 106 1.4 106 1.6 106
0 2 104 4 104 6 104 8 104 1 105
Layer Rates from 2-18-2001 Layer 18 Sums
Layer 17 Sums Layer 16 Sums
La yer Scale r R a te s (H z) blsc3072
9/22/03 R. Messner 44
Outer Layers versus LER loss monitors Jan 2003
0 5 105 1 106 1.5 106 2 106
0 2000 4000 6000 8000 1 104
ifrtable_l16-l9.2003.01-06.2115.2216 Layer 15 Layer 14 Layer 13 Layer 12 Layer 11 Layer 10 Layer 9 La y e r S c al e r R a te blsc3042
9/22/03 R. Messner 45
The singles rates in the outer forward endcap chambers track the LER loss monitors
blsc3072 looks at the 24m collimator blsc3042 looks at the 12m collimator Note that the loss monitors vary with time
9/22/03 R. Messner 46 PEP beam losses from April 13 thru May 13
9/22/03 R. Messner 47
Physical Layout for the Forward Endcap Scalars
• This view is from the south tunnel, looking north at the face of layer 18
• Enrico’s plots of x-y hits in the layers are also
drawn from this perspective West East Layer 18 18W1 18W2 18W11 18W12 18E1 18E2 18E11 18E12 Module 1 Module 2 Module 3 Module 4 Module 5 Module 6 Module 1 Module 2 Module 3 Module 4 Module 5 Module 6 Top Middle Bottom Top Middle Bottom
Indices 1, 2, ... , 11, 12 Indices 13, 14, ... , 23, 24
Layer 17 will have indices 25, 26, ... , 47, 48 Layer 16 will have indices 49, 50, ... , 71, 72
9/22/03 R. Messner 48
Downstream Collimator with shield
Collimator 3043 and Lead Wall with
Babar in the background
9/22/03 R. Messner 49
Elevation View of the LER beamline
Dipole Magnet
Collimator 3043
The central portion is the angular region exposed by the hole left in the lead wall for the beampipe assuming a particle goes straight
9/22/03 R. Messner 50
Plan View of the LER beamline
1 m
Angular region exposed by the hole left in the lead wall for the beampipe
9/22/03 R. Messner 51
Run 37687
9/22/03 R. Messner 52
Run 33540: Layer 14; blsc3072 ~ blsc3042
9/22/03 R. Messner 53
Run 33864: Layer 14; blsc3072 >> blsc3042
9/22/03 R. Messner 54
Upstream Collimator with shield Collimator 3076 – side view
9/22/03 R. Messner 55
Collimator 3076
Lead Bricks Hole between
Coils Loss Monitor 3072
