Low Luminosity Opportunities

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Low Luminosity Opportunities
Andrew Brandt, U. Texas at Arlington
really hard
easy
DØ ADM November 18, 2005
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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 (lt3.5 months of
  operations left)
• Low lum period gives opportunity to maximize
• diffractive physics during a period of
  limited use
• to rest of experiment

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Low Luminosity Proposal I

• Run 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 extra
• collisions.
• 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 (theyre thinking about it). Duncan
  is looking at timing to
• understand which scenario best. Any implications
  at DØ, lum calc? trigger?

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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

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Elastic t distribution
t range accessible with injection tune
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Total Cross Section
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Total Cross Section Study
Key issues Low enough t for extrapolation Suffici
ent elastics (need 50-100k to have a chance at
2mb error) estimate 300k assuming tmin.15 (50
trigger, 50 f) Inelastic counting (assume
2) Emittance (5-10?)
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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 since it would be the only one at
current energy error drops to 4 to 4.5
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Double Pomeron
2nb-1100ubacctrig eff 2000100.1.510000
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
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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 ? from gaps with ? from
  protons (this allows for example double pomeron
  with trackgap, 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, lum
• Proposal take one store at beginning of two week
  period, look at data and if justified take more
  data in second week

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Low Luminosity Luminosity
CDF
Expect 40-100 nb-1 for a 24 hour store
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CDF Low Luminosity Proposal
Context Tokyo pots will be removed during
shutdown in favor of collimators to protect
silicon
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Summary

• Request two types of stores to take advantage
  of FPD capabilities during a rare
• lowish luminosity running period
• I) High ? for low-t elasticdiffraction
• II) Low luminosity for 0 MI calibration sample
  and intermediate t