Far forward angle physics at the LHC E. Norbeck and Y. Onel University of Iowa For the 24th Winter Workshop on Nuclear Dynamics South Padre Island April 2008

24th WW April 11, 2008Ed Norbeck U. of Iowa2

24th WW April 11, 2008Ed Norbeck U. of Iowa3 I will consider here methods of detecting charged particles at such small angles that they sneak through the very forward calorimeter. This means angles less than 0.6º or η > 5.3 Extreme example The FP420 Detectors 3 mm from the beam at a distance of 420 m from the IP 7 microradians =.0004º

24th WW April 11, 2008Ed Norbeck U. of Iowa4 “By detecting protons that have lost less than 1.5% of their longitudinal momentum, a rich electroweak, Higgs, beyond the Standard Model and QCD program becomes accessible, with the potential to make measurements which are unique at LHC, and difficult even at a future linear collider. By tagging both outgoing protons in the process pp → p + X + p, the LHC is effectively turned into a glue-glue collider.” Why would one want detectors at 420 m?

24th WW April 11, 2008Ed Norbeck U. of Iowa5 Match the two protons to event in CMS Measuring arrival time to 10 ps of both protons will identify the interaction point to 3 mm. 0.5º C will change the length of 420 m by 3 mm Can use the tracker to recalibrate for slow drifts. A 250 GeV proton would be 10 ps late.

24th WW April 11, 2008Ed Norbeck U. of Iowa6 Will the detectors at 420 m be useful with heavy ions? The question is still under discussion. Some say yes and provide specific examples. Others say it is unnecessary because 50% of the time an ultraperipheral reaction can be tagged by a neutron in a ZDC. A lead ion is easily broken up. The 420 m detectors should be useful for p-Pb studies.

24th WW April 11, 2008Ed Norbeck U. of Iowa7 ZDC (Zero-Degree Calorimeter) A ZDC at CMS is similar to those at RHIC Difference is that it must be located deep inside of the TAN (which is 140 m from the IP)

24th WW April 11, 2008Ed Norbeck U. of Iowa8

24th WW April 11, 2008Ed Norbeck U. of Iowa9

24th WW April 11, 2008Ed Norbeck U. of Iowa10 Quartz fiber bundle PMT Quartz fiber bundle PMT Beam Pipe Magnet Go to larger angles by looking at particles near the beam pipe at distances 50 to 100 m from IP. Will see showers from deflected beam particles hitting the beam pipe. Will also see beam-air events and beam halo. Want to distinguish incoming from outgoing particles. Δt < 12.5 ns for protons. One idea making use of the directionality of Čerenkov radiation

24th WW April 11, 2008Ed Norbeck U. of Iowa11

24th WW April 11, 2008Ed Norbeck U. of Iowa GeV pions from TB04 test of HF While analyzing TB04 data during the summer of 2005, abnormally high energy events were seen in several pion runs. HF is ~10 λ int thick e -10 = 1/22026 A PMT is an excellent charged particle detector (Čerenkov light in front face)

24th WW April 11, 2008Ed Norbeck U. of Iowa13 Use PMTs as the directional detectors. Duct-tape PMTs to beam pipe. (Requires too many PMTs– excessive electronics) QuartzQuartz Black APDs Frosted or coated with wavelength shifter Latest idea (avalanche photodiodes) (second in anticoincidence)

24th WW April 11, 2008Ed Norbeck U. of Iowa14 TOTEM T2 CASTOR HF

24th WW April 11, 2008Ed Norbeck U. of Iowa15

24th WW April 11, 2008Ed Norbeck U. of Iowa16 CASTOR layout IP

24th WW April 11, 2008Ed Norbeck U. of Iowa17 CASTOR 3-D view

24th WW April 11, 2008Ed Norbeck U. of Iowa18 CASTOR I is under construction Iowa hopes to have funds by this summer for CASTOR II Will it be a copy of CASTOR I with better longitudinal resolution or a new design?

24th WW April 11, 2008Ed Norbeck U. of Iowa19 The TOTEM T2 telescope T2 is not a calorimeter—no absorbers The detectors use the triple-GEM technology

24th WW April 11, 2008Ed Norbeck U. of Iowa20 Structure of a triple-GEM detector (Gas Electron Multiplier) The readout board has small pads that collect the electrons In TOTEM T2 the pad readout is digital—one bit per pad If the pad signal is above threshold get a 1, otherwise a 0 Each of the 10 layers has about 3000 pads

24th WW April 11, 2008Ed Norbeck U. of Iowa21. Particles in a small digital calorimeter 8 GeV π+ event (early shower)A single muon Can get better energy resolution by not measuring the energy!!

24th WW April 11, 2008Ed Norbeck U. of Iowa22 Consider for CASTOR II 40 layers of tungsten with triple-GEMs with pads per layer As a digital calorimeter the data bits should be manageable even at this late date. Should work well with pp experiments For PbPb the occupancy is too large, even with pads/layer. We are open to new ideas.