CMS Hadronic Forward Calorimeter Restoration of Functionality Iowa, BU, FNAL

severe descoping of HF in 2002 $$ for HB, tracker

tail catcher for late developing hadronic showers - eliminated

½ of quartz fiber gone, quartz cladding replaced with plastic

fiber diameter doubled…2x coarser sampling

insufficient to see muons, the natural calibration…5 GeV/pe

(no other detector in front or behind to cross-correlate)

air light guides from beam region to PM’s outside calorimeter - cutPMs directly in the path of π’s from penetrating showers & from μ’s

fasting timing (1 ns) interpolator removed, cannot kill out of time background

metal envelope, thin-windowed PMs eliminatedinstead thick, all glass PMs

on HF Task Force to ameliorate much of this, some asap, others at Upgrade I

2006 – 2009 HF CERN Summer Test Beam Studies BU team

TB 06 &07 serious problem revealed in CMS mockup in CERN HF Test Beam Cherenkov light from π’s and μ’s traversing PM glass cause

large false high energy depositions…up to 4 TeV equivalent w/ Freeman

critical to physics missions of Hadronic very Forward1) missing energy trigger…may swamp the L1 trigger menu2) tagging jets for high mass Higgs searches for the invisible Higgs

e.g. proposed BU thesis Lawson

TB 08 inserted scintillating crystal tags w/Freemanlong time constant light separable from fast Cherenkov signal?

did not work…scintillation light from thinnest crystals overwhelms Cherenkov

confirmed feasibility of quartz plate tail catcher behind PM box BU

air light guides developed at BUOsborne

prototyped perfected at BU cosmic tower

TB 09 evaluated 4-anode mesh dynode PMs w/Iowa, Fairfield

(and SiPM evaluations also perfected in these Test Beam runs)

1” square, mesh dynode PM…a 1 to 1 replacement for current tube

43% quantum efficiency, makes up for x2 loss of quartz, can calibrate muons

thin front window (~0.5mm), no glass on sides…cuts Cherenkov background tails

4 anodes…tags thru muons, and corrects energy measurement

HF mockup & SiPMs in CMS test beam line at CERN, summer ’09

with µ beam parallel to PM window…

raw PM rate ~20 x bigger with current PM that with mesh PM pulse height 2-5 x bigger than with beam perpendicular

tag Cherenkov window events…and correct energy measurement

corrected energy = 4/3 energy in non-tagged anodesworks beautifully...1 box of 8 PMs to be installed in February

RESERVE

Normalization/calibration:

Single PMT and 4 tower

readout on calorimeter:

HF PMT: R7525

Mini: R9880U-110

4Anode: R7600U-200-M4

1Anode: R7600U-200

150 GeV Muons into PMT at 90°