Low Luminosity OpportunitiesAndrew Brandt, U. Texas at Arlington

DØ ADM November 18, 2005

“easy” “really hard”

Context• FPD fiber trigger now working, gives possibility of

unique data samples

• FPD will only operate routinely up until shutdown, primarily due to increased luminosity expected after shutdown (<3.5 months of operations left)

• Low lum period gives opportunity to maximize

diffractive physics during a period of limited use

to rest of experiment

Low Luminosity Proposal IRun with injection tune (*=1.6m), 1 p on 4 pbar (originally 2x4 but CDF not interested), no low squeeze, collisions by ramping down separator voltages. This particular configuration is required to minimize setup time and extracollisions.

Note: If we collide P1 and A1 at DØ, P1 will collide with A2 60m later (at D1)with A3 120m later, with A4 180m later. If we collide P4 with A4, P4 will collide with A1 180m earlier (C side), etc.They (AD) have some tricks to lop off last or first bunch, may be able to scrape other bunches (they’re thinking about it). Duncan is looking at timing to understand which scenario best. Any implications at DØ, lum calc? trigger?

Low Lum Proposal I: “High ”

Why: Can move pots to much lower t-values (high * means fatter beams at IP and not as fat at pots) Physics goals: Low-t elastic scattering (map out dip region), low-t single diffractive and double pomeron. Totally unique data samples.

Possibility of total cross section measurement.

Stats needed: Minimum one store (estimate 1-2 nb-1 for a store) uncertainties in initial lum and pot positions make predictions difficult.

Proposal: Take one store at beginning of two week period, look at data and if justified take more data in second week

Elastic t distribution

t range accessible with injection tune

pot position integ. luminosity

Total Cross Section

DØ

Total Cross Section Study

Key issues:Low enough t for extrapolationSufficient elastics (need 50-100k to have a chance at 2mb error)estimate 300k assuming tmin=.15(50% trigger, 50% φ)Inelastic counting (assume 2%)Emittance (5-10)

PU 8

50k events

0.1 0.2 0.5

Luminosity Uncertainty Brendan says:scenario 1 :----------------we measure cross section half way between CDF and E811 with comparable errors- exactly same experimental error as now

The luminosity error would decrease from 6.5% down to about 6%

scenario 2:----------------we measure a cross section consistent with CDF with comparable errors- a new Tevatron average is formed using only CDF and D0 -exactly same experimental errors as now

The luminosity error would decrease to 5%

Alternate Scenario (not Brendan): adopt DØ uncertainty sinceit would be the only one at current energy; error drops to 4 to 4.5%

Double Pomeron 2nb-1*100ub*acc*trig eff =2000*100*.1*.5=10000 events?

Could be used to distinguish different models of pomeron (phi correlations of p and pbar for example:A. Kupco, R. Peschanski, C. Royon, Phys. Lett. B606 (2005) 139

Low Luminosity Proposal II

Run with *=0.28 m at low lum (few E30) (This is equivalent to CDF proposal)

Why: ~0 multiple interactions, low halo allows closer pot positions, intermediate t

Physics goals: calibrate ξ from gaps with ξ from protons (this allows for example double pomeron with track+gap, improving acceptance)

gap/cal studies in low MI environment alignment/calibration for full data sample (using large elastic sample) intermediate t-sample for physics Stats needed: 1-2 stores depending on pot positions, lumProposal: take one store at beginning of two week period, look at data

and if justified take more data in second week

Low Luminosity Luminosity

Expect 40-100 nb-1 for a 24 hour store

CDF

CDF Low Luminosity Proposal

Context:

Tokyo pots will be removed

during shutdown in favor of

collimators to protect silicon

Summary

Request two types of stores to take advantage of FPD capabilities during a rare

lowish luminosity running period: I) High * for low-t elastic+diffraction II) Low luminosity for 0 MI calibration

sample and intermediate t