Toward Assessing HF with Beam Halo Muons BeamGas

Toward Assessing HF with Beam Halo Muons & Beam-Gas Events …tuning HF when beam returns excerpts from US-CMS presentation 9/26/08 Michael Schmitt, NWU work of Cathode Strip Chamber muon group

Cathode Strip Chambers: CSC’s HF-

Minus Muon Endcap

• Muon group analyzed three runs • compared with beam halo MC • 62084: Wed. afternoon, beam 2 50 passes • 62096: Wed. eve, beam 2 hundreds of passes • 62232: Thur. near midnight, beam 2 captured. • Muon trigger • “hit” CSC chamber = rechits in at least four layers out of six

LHC Beam Notation +y +z CMS LHC “Beam 1”: +x • Enters p 5 from p 4 • Traverses CMS from ME+ to ME LHC “Beam 2”: • Enters p 5 from p 6 • Traverses CMS from ME to ME+

Sept. 5 th to 7 th & 9 th +y +z • Machine +x – Beam 2 injected IP 8 • • Threaded to dump in IP 6 Steered then inject and dump – Beam 1 injected IP 2 • • Threaded through to collimators in IP 5 CMS Tues, 9 -Sept – 20 shots of Beam 1 onto collimator 150 m upstream of CMS – Large CSC events require CSC (reduced HV for subsequent dumps) Traverses CMS from ME+ to ME

First Events: Collimators Closed ~2 x 109 protons on collimator ~150 m upstream of CMS HO, HF - dark blue; HB, HE - light blue; ECAL- pink; Muon - green; Tracker & Magnet Off ~200 muons per cm 2

Sept. 10 th : 27 km/hr (Aymar) • Machine: – Beam 1 injected IP 2 • Threaded around the machine in 1 h • Trajectory steering gave 2 or 3 turns – Beam 2 injected IP 8 • Threaded around the machine in 1 h 30 • Trajectory steering gave 2 or 3 turns • Q and Q’ trims gave a few hundred turns • CMS – Big splash events observed when beam onto collimators (as before) - 100 -1000 Te. V observed in ECAL-HCAL DQM gave information instantly – Halo muons observed once beam started passing through CMS with the CSCs and Calos • Prompt analysis from CSC fully reconstructed muons on real time September 10

First beam: many events with a large number of hit chambers beam 1

fan-like, several tracks on incident side, a little on the other. beam 1

particles do not shower in muon iron yokes: muons beam 2 (early) very clean chambers…little noise

many very clean events reconstruct muons through entire CMS detector

events with 2 or 3 muons:

muons reconstruct across 20 m w/o beam alignment

What do muon triggers look like in HCal? muon track does pass through the tower with the high energy measurement.

Beam-Halo: HE+Muon CSC Run 62096 Event 598642 S. Won • Time distribution of HE-matched hits may be useful for rejection of halo hits in the future Run 62096 Event 4632 S. Won

Beam - Gas events hit HF+ f h HF- Beam Direction HF+

Summary: muon and beam gas data look good thousands of clean, well-reconstructed beam halo events are available linked with Schmitt to assess HF (with Lawson and Carleton)