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 1033 Hz/cm2

SD ~ 10 mb / sidemin ~ 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: TCP @ 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 GeV2 < |t| < ~ 6.5 GeV2

- hard diffraction with CMS: RP 220: D = 83 mm , xmin ~ 28 ~ 2.7 mm min = 3 % RP 147: D = 70 mm , xmin ~ 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 Hz @ L = 1033 cm-2 s-1

(V) [mm] (H) [mm] (for n = 2.5 m rad)

RP 147 0.85 0.50 no reference from 2011 but large beam big tolerance

RP 220 0.40 0.095 very small (H) need to align with small steps

Dijet Cross-Section

1nb

1b

Scenario for * = 90 m

(V) [mm] (H) [mm] (for n = 2.5 m rad)

RP 147 0.44 0.32 no reference from 2011

RP 220 0.67 0.43 use 2011 alignment as first guess

Two runs:1. Alignment and minimum bias physics

• bunches: 2 coll. + 1 non-coll., with 6 x 1010 p/b• n = 2 m rad

Option (a): Full scraping exercise for 24 pots (up to 12 hours) operation with Vertical RP @ 5 = TCP + 0.5 mm) Horizontal RP @ 10 (protected by TCSG @ 6 and TCDQ @ 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 1027 cm-2 s-1 / b, = 0.05

Scenario for * = 90 m

2. Diffractive dijets (DPE) with CMS• 156 bunches with 6 x 1010 p/b• n = 2 m rad

• Collimation hierarchy: Vertical: TCP @ 4.5 , TCSG @ 6 – 6.5 , RP @ 8 – 8.5 Horizontal: in addition TCDQ @ 8 , RP @ 10

• Alignment already done fast approach (~ 1 h)• Trigger: (RP double arm) x dijet (> 20 GeV):

diff. dijet : ~ 0.5 b3 h data taking ~ 10 nb-1

L = 1.2 x 1030 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 @mWorst case for RP 220: T – B > 2 x @m

If no mechanical solution for this year: take data for both diagonals separately