# Presentation: 665786

## LHC Startup Luminosity Planning

- July 29, 2005

## References

- Background on LHC
- _[http://ab-div.web.cern.ch/ab-div/Publications/LHC-DesignReport.html](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](http://indicodev.cern.ch/conferenceDisplay.py?confId=044)_
- Other
- _[http://dpnc.unige.ch/seminaire/talks/bruning.pdf](http://dpnc.unige.ch/seminaire/talks/bruning.pdf)_
- _[http://www.agsrhichome.bnl.gov/LARP/050406_danfords/](http://www.agsrhichome.bnl.gov/LARP/050406_danfords/)_
- _[http://www.agsrhichome.bnl.gov/LARP/050406_danfords/pres/Bailey01.pdf](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](http://agenda.cern.ch/askArchive.php?base=agenda&categ=a053001&id=a053001s1t2%2Ftransparencies%2FgplhccJun2005.ppt)_

## 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

| Nominal Parameters |  |
| --- | --- |
| Beam energy (TeV) | 7.0 |
| Number of particles per bunch | 1.15 1011 |
| Number of bunches per beam | 2808 |
| Time between crossings(ns) | 25 |
| Crossing angle (rad) | 285 |
| Nomalised transverse emittance (m rad) | 3.75 |
| Beta function at IP 1, 2, 5, 8 (m) | 0.55,10,0.55,10 |

| Luminosity in IP 1 & 5 (cm-2 s-1) | 1034  |
| --- | --- |
| Luminosity in IP 2 & 8 (cm-2 s-1) | ~5 1032 |
| Transverse beam size at IP 1 & 5 (m) | 16.7 |
| Transverse beam size at IP 1 & 5 (m) | 70.9 |
| Stored energy per beam (MJ) | 362 |

## 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)

- 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)

- 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

- 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

- 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

| Beam energy (TeV) | 6.0, 6.5 or 7.0 | 6.0, 6.5 or 7.0 | 6.0, 6.5 or 7.0  |
| --- | --- | --- | --- |
| Number of bunches per beam | 43 | 43 | 156 |
| * in IP 1, 2, 5, 8 (m) | 18,10,18,10 | 2,10,2,10 | 2,10,2,10 |
| Crossing Angle (rad) | 0  | 0  | 0  |
| Transverse emittance (m rad) | 3.75  | 3.75 | 3.75 |
| Bunch spacing (s) | 2.025  | 2.025 | 0.525 |
| Bunch Intensity | 1 1010  | 4 1010  | 4 1010  |
| Luminosity IP 1 & 5 (cm-2 s-1) | ~ 3 1028 | ~ 5 1030 | ~ 2 1031 |
| Luminosity IP 2 (cm-2 s-1) | ~ 6 1028 | ~ 1 1030 | ~ 4 1030 |

## 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

| Beam energy (TeV) | 6.0, 6.5 or 7.0 | 6.0, 6.5 or 7.0 | 6.0, 6.5 or 7.0  |
| --- | --- | --- | --- |
| Number of bunches per beam | 936 | 936 | 936 |
| * in IP 1, 2, 5, 8 (m) | 2,10,2,10 | 0.55,10,0.55,10 | 0.55,10,0.55,10 |
| Crossing Angle (rad) | 250  | 285  | 285  |
| Transverse emittance (m rad) | 3.75  | 3.75 | 3.75 |
| Bunch Intensity | 4 1010  | 4 1010  | 9 1010  |
| Luminosity IP 1 & 5 (cm-2 s-1) | ~ 1 1032 | ~ 4 1032 | ~ 2 1033 |
| Luminosity IP 2 & 8 (cm-2 s-1) | ~ 2 1031 | ~ 2 1031 | ~ 1 1032 |

## 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

| Beam energy (TeV) | 6.0, 6.5 or 7.0 | 6.0, 6.5 or 7.0 | 7.0  |
| --- | --- | --- | --- |
| Number of bunches per beam | 2808 | 2808 | 2808 |
| * in IP 1, 2, 5, 8 (m) | 0.55,10,0.55,10 | 0.55,10,0.55,10 | 0.55,10,0.55,10 |
| Crossing Angle (rad) | 285  | 285  | 285  |
| Transverse emittance (m rad) | 3.75  | 3.75 | 3.75 |
| Bunch Intensity | 3 1010  | 5 1010  | 1.15 1011  |
| Luminosity IP 1 & 5 (cm-2 s-1) | ~ 7 1032 | ~ 2 1033 | 1034 |
| Luminosity IP 2 & 8 (cm-2 s-1) | ~ 4 1031 | ~ 1 1032 | ~ 5 1032 |

**Long shutdown (6months)**

- After shutdown

## Typical Year

## The First Years?

- 2007

- 2008

- 2009

- 2010

- 2011

- ~ 3 1028

- ~ 2 1031

- ~ 1 1032

- ~ 4 1032

- ~ 2 1033

- ~ 7 1032

- ~ 2 1033

- ~ 5 1033

- ~ 5 1033

- 1034

- If one takes the luminosities from previous.....

## 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

| Channel | # of Events |
| --- | --- |
| W -> μ | 7000 |
| Z -> μμ | 1100 |
| t tbar -> μ + X | 80 |
| QCD jets PT>150 GeV | 1000(for 10% of trigger bandwith) |
| Minimum bias | Trigger limited |
| gluino-gluino, M~ 1TeV | 1-10 |

- Taken from table in hep-ph/0504221

## 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

- From Polesello’s Talk to LHCC in June

## “Minimum Bias”

***1000 events***

- 

**dN****ch****/d******

**dN****ch****/dp****T**

- Comparison of generated charged particles with reconstructed tracks_** **_

**Black =   Generated (Pythia6.2)**
**Blue   =   TrkTrack: iPatRec**
**Red    =   TrkTrack: xKalman**

**Only a fraction of tracks reconstructed, because:**
**limited rapidity coverage**
**can only reconstruct track p****T**** with good efficiency down to ~500MeV**

**Previous dN****ch****/d******** measurements published for p****T**** > 0, so need to apply correction factor. Biggest systematic uncertainty?**
**Explore special runs with reduced solenoidal magnetic field?**

**Reconstruct tracks with:**
**   ****1) pT>500MeV**
**   ****2) |d****0****| < 1mm**
**   ****3) # B-layer hits >= 1**
**   ****4) # precision hits >= 8**

**p****T**** (MeV)**

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

- 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
- ~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

*Require M**w** within 10 GeV of nominal W mass*

- S/B = 1.77

**Top mass (GeV)**

***m(t)***

- 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

- Selection cuts: ETmiss > 20 GeV, 1 lep Pt > 20 GeV, 4 jets Pt > 20 GeV
- No trigger selection efficiency taken into account yet

- Top for about 300 pb-1

- Slide from Polesello at LHCC