Lhc startup luminosity planning
This presentation is the property of its rightful owner.
Sponsored Links
1 / 20

LHC Startup Luminosity Planning PowerPoint PPT Presentation


  • 44 Views
  • Uploaded on
  • Presentation posted in: General

LHC Startup Luminosity Planning. July 29, 2005. References. Background on LHC http://ab-div.web.cern.ch/ab-div/Publications/LHC-DesignReport.html Relatively recent workshop (Chamonix in January 2005) http://indicodev.cern.ch/conferenceDisplay.py?confId=044 Other

Download Presentation

LHC Startup Luminosity Planning

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Lhc startup luminosity planning

LHC Startup Luminosity Planning

July 29, 2005


References

References

  • Background on LHC

    http://ab-div.web.cern.ch/ab-div/Publications/LHC-DesignReport.html

  • Relatively recent workshop (Chamonix in January 2005)

    http://indicodev.cern.ch/conferenceDisplay.py?confId=044

  • Other

    http://dpnc.unige.ch/seminaire/talks/bruning.pdf

    http://www.agsrhichome.bnl.gov/LARP/050406_danfords/

    http://www.agsrhichome.bnl.gov/LARP/050406_danfords/pres/Bailey01.pdf

    Have stolen liberally from last reference above

  • Some references on early physics (not necessarily so early…)

    • Some previous talks at these Friday meetings(Ian, Andreas….)

    • hep-ph/05044221

    • Talk by Polisello at recent LHCC meeting http://agenda.cern.ch/askArchive.php?base=agenda&categ=a053001&id=a053001s1t2%2Ftransparencies%2FgplhccJun2005.ppt


Introduction and disclaimer

Introduction and Disclaimer

  • The talk has a narrow scope

  • Not pedagogical regarding LHC

  • LHC startup is obviously very complex but I will ignore all of the complexity and focus on stated luminosity goals

  • Luminosity will likely vary by orders of magnitude in first year or more of operation, so plenty of room to be wrong in predictions!

  • Purpose is to (hopefully) initiate thinking locally (and maybe some work) on very, very early physics eg. from pilot run

  • Warning: I’m a pessimist about luminosity…..


Design goals

Design Goals


Early conditions

Early Conditions

  • Compared to design conditions…………….

  • Beam energy very likely below 7 TeV.

    • 6 TeV?

    • 6.5 TeV?

  • Fewer protons per bunch

  • Many fewer bunches

  • Head-on collisions

  • Much larger *(less “squeeze”)

  • On-time for physics much less (same for detector no doubt)

  • Primary goal of first (pilot) run – achieve and sustain collisions, start understanding of machine.


How to get started i

How To Get Started(I)

  • Avoid quenches (and damage)

    • Reduce total current to reduce stored beam energy

      • Lower ib

      • Fewer bunches

    • Higher * to avoid problems in the (later part of) the squeeze

    • Reduce energy to get more margin

      • Against transient beam losses

      • Against magnet operating close to training limit

  • Both machine and experiments will have to learn how to stand running at nominal intensities

  • An early aim is to find a balance between robust operation and satisfying the experiments

    • Maximize integrated luminosity

    • Minimize event pile-up


How to get started ii

How To Get Started(II)

  • Electron cloud ( LHC simulations and SPS experience )

    • ib < 35% nominal for 25ns spacing

    • ib ~ nominal for > 50ns

  • With lower currents in mind, two machine systems will be staged

    • Only 8 of 20 beam dump dilution kickers initially installed

      • Total beam intensity < 50% nominal

      • Install the rest when needed

    • Collimators ( robustness, impedance and other issues )

      • Phased approach

      • Run at the impedance limit during phase I

        • Lower currents

        • Higher *


Planning

Planning

  • Phase I collimators and partial beam dump

    • Pilot physics run with few bunches

      • No parasitic bunch crossings

      • Machine de-bugging no crossing angle

      • 43 bunches, unsqueezed, low intensity

      • Push performance (156 bunches, partial squeeze, higher intensity)

    • 75ns operation

      • Establish multi-bunch operation

      • Relaxed machine parameters (squeeze and crossing angle)

      • Push squeeze and crossing angle

    • 25ns operation with Phase I collimators + partial beam dump

      • Needs scrubbing for higher intensities ( ib > 3 1010 )

  • Phase II collimators and full beam dump

    • 25ns operation

      • Push towards nominal performance


Stage 1 pilot run luminosities

Stage 1 – Pilot Run Luminosities

  • No squeeze to start

  • 43 bunches per beam (some displaced in one beam for LHCb)

  • Around 1010 per bunch

  • Push one or all of

    • 156 bunches per beam (some displaced in one beam for LHCb)

    • Partial optics squeeze

    • Increase bunch intensity


Stage 2 75ns luminosities

Partial squeeze and smaller crossing angle to start

Luminosity tuning, limited by event pileup

Establish routine operation in this mode

Move to nominal squeeze and crossing angle

Increase bunch intensity ?

Tune IP2 and IP8 to meet experimental needs

Stage 2 – 75ns Luminosities


Stage 3 25ns luminosities

Production physics running

Start with bunch intensities below electron cloud threshold

Scrubbing run (1-2 weeks)

Increase bunch intensities to beam dump & collimator limit

Install beam dump kickers

Install phase II collimators

Increase bunch intensities towards nominal

Tune IP2 and IP8 to meet experimental needs

Stage 3 – 25ns Luminosities

Long shutdown (6months)

After shutdown


Typical year

Typical Year


The first years

The First Years?

2008

2009

2010

2011

2007

~ 7 1032

~ 5 1033

1034

~ 3 1028

~ 2 1031

~ 1 1032

~ 2 1033

~ 2 1033

~ 5 1033

~ 4 1032

If one takes the luminosities from previous…..


Pilot run integrated luminosity

Pilot Run Integrated Luminosity?

  • Very hard to estimate.

  • Efficiency factor(colliding beam time of machine and ATLAS working together) 10%? 20%...who knows

  • Optimistic??? Pessimistic??? guess would be about 1030 for about 30 days or very roughly 1 pb-1

  • In my opinion, useful to understand what physics can be done with 0.1, 1, 10 pb-1 soon. Limited scope of study.


Some rates for 1 pb 1

Some Rates for 1 pb-1

Taken from table in hep-ph/0504221


Follow on

Follow On

  • Some studies have been done (see Rome meeting) that could be used as as starting point for “≤1-10pb-1 physics” investigations

    • Minimum bias dN/d and so forth

    • W and Z production

    • Jets

  • I think would be good idea to systematically go through these in the next few months…


Extra stuff

Extra Stuff

From Polesello’s Talk to LHCC in June


Minimum bias

“Minimum Bias”

dNch/d robust measurement: do not need full ID reconstruction

1000 events

dNch/d

Comparison of generated charged particles with reconstructed tracks

  • Only a fraction of tracks reconstructed, because:

    • limited rapidity coverage

    • can only reconstruct track pT with good efficiency down to ~500MeV

h

Black = Generated (Pythia6.2)

Blue = TrkTrack: iPatRec

Red = TrkTrack: xKalman

dNch/dpT

Reconstruct tracks with:

1) pT>500MeV

2) |d0| < 1mm

3) # B-layer hits >= 1

4) # precision hits >= 8

  • Previous dNch/d measurements published for pT > 0, so need to apply correction factor. Biggest systematic uncertainty?

  • Explore special runs with reduced solenoidal magnetic field?

pT (MeV)


Lhc startup luminosity planning

Studies on W production

  • Large statistics

  • Basic benchmark process to check our ability to perform measurements

  • Aim at constraining proton PDFs

  • Emphasis on understanding systematic detector effects

  • Rome Production W+/- -> e+/- Sample

    • HERWIG + CTEQ5L, U.E. with Jimmy

    • ~67K fully simulated events (5 pb-1).

    • Analysis performed with new ATLAS analysis tools

  • Concentrate on rapidity variables sensitive to PDF parametrisations and uncertainties

    • W->e Rapidity distributions at GEN and DET Level

    • W->e Asymmetry and Ratio at GEN and DET Level

  • Preliminary evaluation of charge misassignment systematics


Top for about 300 pb 1

Top for about 300 pb-1

Selection cuts: ETmiss > 20 GeV, 1 lep Pt > 20 GeV, 4 jetsPt > 20 GeV

No trigger selection efficiency taken into account yet

Require Mw within 10 GeV of nominal W mass

m(t)

S/B = 1.77

Top mass (GeV)

Top peak clearly visible after 1 week of LHC data(NOT AT 1030!!!)

Measured top mass 160.0 ± 1.0 GeV , stat error on xs: 8.3%

Work in progress on systematics

Slide from Polesello at LHCC


  • Login