Running at Low  * and High Lumi Test insertion on 13 October 2011:

Overview of the Insertions H T B BLM (UFO) 15 h

Zoom 6 MHz 4 MHz 2 MHz 0 Expected rate in H from SD: L = 1.5 x Hz/cm 2  SD ~ 10 mb / side  min ~ 3 mm / 7 cm ~ 5 %  SD (visible) ~  SD x (1 decade / 6.5 decades) ~ 1.5 mb Rate ~ 2 MHz  correct order of magnitude

Scenario for  * = 0.7 m Minimum RP approach compatible with BLMs : V : 14  H : somewhere between 21  (would dump) and 28  (ok)  conservatively assume 28  Aim at a faster RP beam-based alignment: right after the collimator setup: 4  drive RPs quickly to 6  (except RP 220 H)   if the beam edge is not hit, the alignment is known within ± 2  Physics: - large |t| elastic scattering (vertical pots with SD region cut away) : 3.5 GeV 2 < |t| < ~ 6.5 GeV 2 - hard diffraction with CMS: RP 220: D = 83 mm, x min ~ 28  ~ 2.7 mm   min = 3 % RP 147: D = 70 mm, x min ~ 28  ~ 14 mm   min = 20 % (Is this useful ? Don’t align ?) Trigger: RPs (double arm) x CMS dijet: above 100 GeV:  min = 200 GeV / 8 TeV = 2.5 % diff. dijet cross-section: ~ 1 nb  rate ~ 1 L = cm -2 s -1  (V) [mm]  (H) [mm](for  n = 2.5  m rad) RP no reference from 2011 but large beam  big tolerance RP very small  (H)  need to align with small steps

Dijet Cross-Section 1nb 1b1b

Scenario for  * = 90 m  (V) [mm]  (H) [mm](for  n = 2.5  m rad) RP no reference from 2011 RP use 2011 alignment as first guess Two runs: 1. Alignment and minimum bias physics bunches: 2 coll. + 1 non-coll., with 6 x p/b  n = 2  m rad Option (a): Full scraping exercise for 24 pots (up to 12 hours)  operation with Vertical 5  = TCP mm) Horizontal 10  (protected by 6  and 8  ) Option (b): Faster alignment (without touching the beam) (difficult for RP 147: where to start ?)  operation with retraction by additional 2  4 hours data taking: - 2 hours: min. bias with CMS, trigger on T2 + RP(single arm) with 1 bunch - 2 hours: RP trigger alone (single or double arm) with 2 bunches At the end: loss map for qualification for more bunches L = 7.6 x cm -2 s -1 / b,  = 0.05

Scenario for  * = 90 m 2. Diffractive dijets (DPE) with CMS 156 bunches with 6 x p/b  n = 2  m rad Collimation hierarchy: Vertical: 4.5 , 6 – 6.5 , 8 – 8.5  Horizontal: in addition 8 , 10  Alignment already done  fast approach (~ 1 h) Trigger: (RP double arm) x dijet (> 20 GeV): diff. dijet : ~ 0.5  b 3 h data taking ~ 10 nb -1 L = 1.2 x cm -2 s -1 / b,  = 0.05

Scenario for  * = 500 m Aim at physics near the end of the running season, but optics development earlier in MDs. Technical problem (mitigation possibilities currently being investigated) : Anti-collision switch limits relative Top – Bottom pot distance. Best case for RP 220: T – B > 2 x 7    m Worst case for RP 220: T – B > 2 x    m If no mechanical solution for this year: take data for both diagonals separately