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CMS Longitudinal View
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APS April2000APS April2000MeetingMeeting
Ahmet Sedat AyanDept. of Physics & Astronomy
University of Iowa
Why HF?Why HF?
Covers the pseudorapidity range 3-5 HF psedorapidity range 4.5-5 will get
100Mrad/year. Therefore the detector should be able to withstand this exceptionally high radiation field.
Two main objectives :1. To improve the measurement of the missing
transverse energy EmissT
2. To enable identification and reconstruction of very forward jets
CMS Longitudinal ViewCMS Longitudinal View
HFHF
Calibration
Readout Boxes
Photo detectors
Transporter
FE, Trig/DAQDCS, Voltage
Shielding
Absorber
OpticsQuartz Fibers
HF Transverse HF Transverse SegmentationSegmentation
QQ/QP Border
3 < < 5HF is segmented in = = 0.175
EM (31/20-deg)HAD (25/20-deg)TC(13/20-deg)TOTAL(69/20-deg)
The active region extends from r=12.5 cm to 130 cm.The depth is 165 cm (Fe).
Experimental TechniqueExperimental Technique
•Light is generated by Cherenkov effect in quartz fibers•Sensitive to relativistic charged particles (Compton electrons...)
•d2N/dxdl=2paz2(sin2q/l2)• =(2paz2/ l2 )[1-1/b2n2]• bmin = 1/n• Emin ~ 200 keV
•Amount of collected light depends on the angle between the particle path and the fiber axis
HF PPP1 Side ViewHF PPP1 Side View
Fiber Bundles(EM, HAD and
TC)300-micron core
QP
Ferrules
ROBox( Light Guides)
R6425 PMTs
Iron Absorbe
r(9.5 lI)
Radioactive Source
Tubes
3 x 3 Tower structure
(6 cm x 6 cm)
LED, Laser and PIN
PDs
2.5 mm
2.5 mm
TC (30 cm)HAD (143 cm)
EM (165 cm)
HF Longitudinal HF Longitudinal SegmentationSegmentation
EM HAD
TC
Uniformity Scan with Uniformity Scan with ElectronsElectrons
•There is a +/- 6 % response nonuniformity to electrons due to fiber periodicity at every 2.5 mm (5 mm for EM).
Response to Electrons Response to Electrons and Pionsand Pions
•HF PPP1 responds linearly within 1% to electrons in the energy range tested (6 – 200 GeV). The pion (neg) response is highly nonlinear.
Electromagnetic Energy Electromagnetic Energy ResolutionResolution
Electromagnetic energy resolution is completely dominated by photostatistics (Np.e.). The usual parametrization, a/sqrt(E) + b, results in a~192% and b~9% for the PPP1. 0.85% fiber fraction degrades the EM energy resolution by a ~sqrt(2) compared to HAD95 (1.6%).
137%/sqrt(E) with 1.6% fiber packingFraction (HAD95)
Hadronic Energy Hadronic Energy ResolutionResolution
Hadronic energy resolution is dominated by non-stochastic processes at higher energies. Photo statistics becomes important only at lower energies. The intrinsic energy resolution can be expressed as c-d*ln(E). The expected energy resolution at 1 TeV is 18%.
FLUKAFLUKA CalculationsCalculations
Recent radiation background simulations show improvement in the design of the shielding around the PMT region by a factor of ~two. There is no issue with the radiation dose or neutron flux where the PMTs are located.
All neutrons 2.54x1012
Neutrons (E>100KeV) 1.63x1012
Neutrons (E>20 MeV) 5.12x1011 Ch. Hadrons 2.26x1010
Muons 4.65x109
Photons 1.53x1012
Dose 7 krad
OpticsOptics: FiberFiber RadiationRadiation DamageDamage
Several quartz fiber irradiation studies have been carried out in the last several years. The induced attenuation profile shows that there is less absorbtion in 400-500 nm (PMT) region compared to either shorter or longer wavelengths.
~200 MRad
63% loss
PPP-I SummaryPPP-I Summary
1% linearity in response to electrons. Highly non-linear to negative pions
Electromagnetic Energy Resolution: 192% 9% Expected Hadronic Energy Resolution at 1TeV is 18% +/- 6% non-uniformity in response to electrons due to fiber
periodicity Suppressed induced radiation damage on fibers in PMT region (400-500nm)