APS April2000 Meeting Ahmet Sedat Ayan Dept. of Physics & Astronomy University of Iowa

Why HF?  Covers the pseudorapidity range 3-5  HF psedorapidity range 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 E miss T 2. To enable identification and reconstruction of very forward jets

CMS Longitudinal View

HF Calibration Readout Boxes Photo detectors Transporter FE, Trig/DAQ DCS, Voltage Shielding Absorber Optics Quartz Fibers

HF Transverse Segmentation QQ/QP Border 3 <  < 5 HF is segmented in  =  = 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 Technique Light is generated by Cherenkov effect in quartz fibers Sensitive to relativistic charged particles (Compton electrons...) d 2 N/dxdl=2paz 2 (sin 2 q/l 2 ) =(2paz 2 / l 2 )[1-1/b 2 n 2 ] b min = 1/n E min ~ 200 keV Amount of collected light depends on the angle between the particle path and the fiber axis

HF PPP1 Side View Fiber Bundles (EM, HAD and TC) 300-micron core QP Ferrules ROBox ( Light Guides) R6425 PMTs Iron Absorber (9.5 l I ) Radioactive Source Tubes 3 x 3 Tower structure (6 cm x 6 cm) LED, Laser and PIN PDs

2.5 mm TC (30 cm) HAD (143 cm) EM (165 cm) HF Longitudinal Segmentation EMHAD TC

Uniformity Scan with Electrons There is a +/- 6 % response nonuniformity to electrons due to fiber periodicity at every 2.5 mm (5 mm for EM).

Response to Electrons and 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 Resolution Electromagnetic energy resolution is completely dominated by photostatistics (N p.e. ). The usual parametrization, a/sqrt(E) + b, results in a~192% and b~9% for the PPP % fiber fraction degrades the EM energy resolution by a ~sqrt(2) compared to HAD95 (1.6%). 137%/sqrt(E) with 1.6% fiber packing Fraction (HAD95)

Hadronic Energy Resolution 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%.

FLUKACalculations FLUKA Calculations  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 neutrons2.54x10 12  Neutrons (E>100KeV) 1.63x10 12  Neutrons (E>20 MeV) 5.12x10 11  Ch. Hadrons2.26x10 10  Muons4.65x10 9  Photons1.53x10 12  Dose7 krad

OpticsFiberRadiation Damage Optics: Fiber Radiation Damage 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 nm (PMT) region compared to either shorter or longer wavelengths. ~200 MRad 63% loss

PPP-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 ( nm)