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

2. 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 E miss T 2. To enable identification and reconstruction of very forward jets

3. CMS Longitudinal View

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

5. HF Transverse Segmentation QQ/QP Border 3 <  < 5 HF 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).

6. 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

7. 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

8. 2.5 mm TC (30 cm) HAD (143 cm) EM (165 cm) HF Longitudinal Segmentation EMHAD TC

9. 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).

10. 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.

11. 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 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 packing Fraction (HAD95)

12. 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%.

13. 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

14. 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 400-500 nm (PMT) region compared to either shorter or longer wavelengths. ~200 MRad 63% loss

15. 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 (400-500nm)