# Presentation: 266483

## f

- On Tevatron Lifetimes,
- Beams,  Luminosity & Spot size

- Paul Lebrun
- Fermilab

***April 4 2003****** ***

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## Study Goals

- Luminosity Lifetime , term by term..Does it add up ?
- Previous studes showed that it does add up, with ~5 to 10%, relative.
- If not, may be the Sync Lite Transverse beam size growth rate are wrong.
- The Pbar scale is still a mystery.
- What if the measured spot size is driven by two terms, a “instrumental constant term” and a beam size term, which change with time during the store.
- => establish that we understand (or not) the transverse size growth rate from luminosity lifetime measurements.

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

##  Sync Lite Beam Transverse Size Growth Rate  Measurements:  Protons, store 2328 

- For the record store, transverse size growth  was actually a bit smaller than usual, may be because the proton lifetime  was not very good. (the emittance already reached it’s quasi saturation value.
- Good Correlation between X and Y (TeV strongly coupled.)

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

##  Sync Lite Beam Transverse Size Growth Rate  Measurements:  Protons, Many Recent stores  

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

##  Sync Lite Beam Transverse Size Growth Rate  Measurements:  AntiProtons, store 2328 

- Pbar transverse size growth rate are smaller than proton.
- Not too surprising (IBS is weaker, due to smaller bunch intensities .. To be tested qunantitatively..
- Or, admittedly, we have a problem with Pbar Sync Lite.

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

##  Sync Lite Beam Transverse Size Growth Rate  Measurements:  AntiProtons, many stores  

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## Effective Transverse Size or Emittance  Rate Changes or Inverse Lifetime.

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## Effective Transverse Size, Components.

- Emittance rate changes are double the size rate changes. The last
- Comes from the the hour glass factor, I.e., k in previous is not
- Constant.

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## Hour Glass Factor.

- Polynomial expression from M. Church
- Beta* assumed to be 35.6  cm. Bunch Length from SBD
- Derivative computed from this polynom

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## Numerically... Making a big difference.. 

- ~ “  ( 8  - 3 – 2 ) %/hour“

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## For more stores..  

- We are looking
- For
- Black –
- Red – Green.
- Large fluctuations.
- What are the errors?

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## Result for ~  10 Recent stores.  

-        There seems to be
- a small deficit (~0.5% per hour) in the measured (Sync Lite, SBD) effective spot size, or emittance.
- Is this signficant?
- On a statistical basis,
- It seems so.

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## Transverse/Longitudinal Growth Rates. 

- The hour glass factor counts! As significant as the transverse growth rate.
- So, to establish a “Pbar problem”, one muse improve on the accuracy of these measurement.
- New SBD software (A. Tollestrup) will help.
- Precision Limited.!

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## For Store 2377 

- Store 2377 is a bit anomalous
- SBD was missing (Front-end or Data Acquisition..)
- Hard to make something out of one store.

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## For Store 2385 

- Error bars from Longitudinal effects not taken into account.

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## Comparison with Vladimir Calculation, store 2385

-  Growth Rate, Emitt.             V. Shiltsev (%/hour)       this work(%/hour)
- =================================================
- Effective emittance                       4.35                               4.13 +- 0.514
- ------------------------------------------------------------------------------
- Pbar, Horizontal                           0.625                              0.124 +- 0.43
- Pbar, Vertical                                  -0.1                               0.575 +- 0.64
- Proton Horizontal                          3.03                               3.30  +- 0.29
- Proton Vertical                                2.78                              2.19 +- 0.83
- Longitudinal                                     -                                  1.56 +- 0.29
- -------------------------------------------------------------------------------
- Total Emitt                                    1.58                               3.10 +- 0.41
- V.S. has a “factor 3 discrepancy”,  Longitudinal effects do not totally explain the difference.

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003

## Tentative Conclusion.  

- Luminosity Lifetime “check-sum” is not quite understood: there seems to be a systematic under-estimation of the measured emittance terms, at the level of 0.5%/hour (~5 % relative)
- We have however no strong, direct  evidence that the Pbar Sync Lite Transverse Size Rate increase is “wrong”.
- Difficult analysis, too many subtractions. Longitudinal effects might be relevant.
- Should compare Pbar SyncLite Growth Rate  with IBS prediction for Pbar. (code is written,  have not had time yet to look at data.. )

- Tevatron Lifetimes  - P. Lebrun

- April 4  2003