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)