Physics reach vs luminosity goal

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Physics reach vs luminosity goal installation
time for the LHC Luminosity Upgrade A first
look

• J.-P. Koutchouk , CERN/AT/MCS
• Thanks to L. Rossi

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1- Introduction

• Factors that govern the integrated
  luminosity are
• The time it takes to reach nominal peak
  luminosity,
• The effective collision time (turn-around,
  faults, unavailabilities injectors,
  electricity, machine studies,
• The details of the luminosity decay during a run.
• Theoretical calculations of any of the
  parameters governing these three aspects (except
  perhaps 3) have to be taken with much caution.
• The CPT theorem (better fit) is a pragmatic
  approach requiring a complexity to be
  evaluated. For control room people, this says a
  lot the complexity of a storage rings is a
  control room concept.

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2.- The Model for the LHC luminosity increase

• Adaptative complexity
• Found in the range 0.9 -gt 4.3 for p-colliders
  with an average of 2.4.
• We shall use a strategy of varying complexity
  depending on the closeness of the luminosity to
  the estimated luminosity goal
• Constant factor linear and quadratic
  dependences on closeness ? c?0.5, 3.5
• asymptotic increase above luminosity goal
• Starting at 5 per year and saturating at 20.

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2.- The Model for the LHC integrated luminosity

• Exponential decay during run
• Including beam-beam, IBS and rest-gas
• Optimal run duration for a 70 minutes turn-around
  time
• Time planned for physics 107 seconds
• Machine availability for physics 80
• Running till 2022.

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Complexity in the case of no upgrade
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Luminosity profile in the case of no upgrade
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Improvement in 1/vN in the case of no upgrade
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Complexity in the case of the reference upgrade
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Luminosity profile in the case of the reference
upgrade
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Improvement in 1/vN in the case of the
reference upgrade
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Physics reach versus Luminosity goal and year of
upgrade

• Assumptions
• Same upgraded beam current kb2, Nb1.7
• Same strategy for the complexity
• Same stop for one year to upgrade the detectors
• Vary the year of upgrade and luminosity goal

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Conclusions

• Working on the complexity appears less
  arbitrary than working directly on luminosity
  profiles.
• LHC should reach the nominal luminosity in 2012
  in a reasonably optimistic scenario.
• From 2014, the improvement in statistics becomes
  modest.
• In the reference scenario where the luminosity
  upgrade was essentially due to the increased
  beam current, 5 years are needed to reach the
  luminosity goal!

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Conclusions

• The 10 increase in peak L yields about a factor
  of two of improvement of the statistics
  (precision physics) in this same scenario.
• The yield of a significantly smaller luminosity
  goal appears then marginal (even if the one year
  shutdown is suppressed).
• The largest potential of improvement is likely to
  be in a minimization of complexity increase
  related to the upgrade this favors very much
  stronger focusing with a new Xing angle LR
  compensation strategy and no or small increase of
  beam current.
• Cooking scenarios and calculations to quantify
  the above.