# Presentation: 018455

## Leslie Groer
Columbia University
New York

All DØ Meeting						August 9, 2002                                                                     

**Columbia University**
**New York**
**All DØ Meeting****	****	****	****	****	****	****August 9, 2002                                                                     **

**Calorimeter Thresholds and You!**

## Why the change?

**Threshold of 2.5 originally chosen somewhat at random**
**Run 1 noise dominated by Uranium and not electronics – very different regime now**
**Jet response, jet widths, taus too skinny etc. all indicate that threshold too high**
**Convoluted with the fact that 1.5 was used for MC generation with somewhat incorrect noise model and no non-linearity effects**
**General consensus from the ID and physics groups that we need to go lower**
**Changed threshold on June 26 from 2.5 to 1.5 **
**First run #158062 (global_CalMuon-7.31)**
**Emergency meetings held in last few weeks due to pressure on the offline**
**Occupancies gone from 5% to 15%**
**NADA, clustering, jet finding algorithms scale as N******** where ********~2-3**
**Will briefly show some of the initial studies and work to relieve pressure on the offline farms**
**Calorimeter Task Force**

## Non-linearity a non-issue

**Not all the charge gets stored in the SCA’s near the edges of its voltage rails (i.e. very low or very high values)**
**This means the gain is different for the first few 100’s of ADC counts out of ~4000 counts (about a factor of 1.5)**
**< ~0.5-1 GeV**
**The “non-linearity” is introduced to account for the different gains to convert ADC ******** GeV**
**In the regime of no-signals, close to pedestal, ****there is no non-linearity**

**Therefore applying the threshold to the pedestal rms before or after the gain correction ****makes no difference**** (but it’s a lot easier to understand if done before)**
**Modeling in the MC is another story...**

**Robert Zitoun**

## Missing ET very sensitive

**Major change of average missing E****T ****when going from 2.5 to 1.5 sigma zero- suppression cut:                From 6-7 GeV to 14-18 GeV, with a wider scattering from run to run. One entry per root-tuple.**
**Also true for RMS(MET)**
**One entry per root-tuple, data from 19****th**** june till 9****th**** of July.**
**Not shown but METx and METy are also skewed further at low threshold**

**Gregorio Bernardi**

**<MET>**

**RMS(<MET>)**

## Missing ET cleanup?

**Missing E****T ****cleanup?**

**450 MeV cell threshold**

**1.5 ******** **

**2.5 ******** **

**100 MeV cell threshold**

**Gregorio Bernardi**

## Calorimeter behavior

**Average occupancy up by factor 4-5**
**                           **_**2.5 **__****_**         **_**1.5**__****_
**Zero-bias      0.9k          6.5k**
**Min-bias        1.4k         7.0k**
**JT_95            1.9k         7.6k**

**Daniel Whiteson has been looking for muons in the calorimeter**
**Initial results from data for matching rate for tight local muons gives**
**52%   1.5******
**46%   1.8******
**37%   2.5******

**Silke Duensing**

## Jet widths

**To correct to data need to add in correct noise modeling to current MC, then apply non-linearity effect and then run through reco where non-linearity correction is applied**

**MC**

**DATA**

**width**

**n90**

**Silke Duensing**

## Jet response and resolution

**Jet response and resolution**

**Correct back almost to full MC after simulating correct noise and non-linearity effects and correction in 1.5******** case**
**Response improves from 80 to 85% for threshold changes of 2.5 to 1.5 but no obvious effect on resolution for 1000 MC events – need more statistics...**

**1.5 ******

**response**

**resolution**

**2.5 ******

**Silke Duensing**

## Offline zero suppression

**calunpdata**** package has been modified to apply offline zero suppression similar to the hardware**
_**calunpdata/rcp/CalUnpToMC.rcp**_**float offline_zero_supp_thresh = 2.5**
**Suppression done in ADC counts before **_**any**_** corrections (non-linearity, gains, etc)**
**There is also suppression available for MC data which adds to the confusion**
**Pedestal threshold file taken from online for a particular calibration run so far**

**Questions of stabilty of rms of pedestals being examined in detail**
**Insensitive to actual pedestal, only its width**
**Harry Melanson will put this on the reco farm within the next few days**
**Subset of global data will be reprocessed with different thresholds (1.5, 1.7, 2.0, 2.5) for studies**

## Pedestal rms stability

**Studying online zero suppression stability to apply offline**
**Could probably implement same thresholds offline as online with not too much work**

## Suppression and L3

**The thresholds have ZERO effect on L1 and L2 triggering or readout**
**Processing time scales linearly in L3 **
**Can apply threshold in MeV before apply filtering algorithms**
**L3 calorimeter unpacking, clustering etc under review by Marumi for optimization**

**Marumi Kado**

## Calorimetry Task Force

_**Members:**_
**Gregorio Bernardi*, Volker Buescher, Christophe Clement*, Silke Duensing, Anna Goussiou*, **
**Leslie Groer (co-chair), Marumi Kado, Nirmalya Parua, Serban Protopopescu, Dean Schamberger, **
**Marek Zielinski (co-chair), Robert Zitoun***
**	****	****	****	****	****	***** = on vacation this week...**
_**Charge:**_
**The task force will determine the zero-suppression threshold for the calorimeter readout.  In order to fully **
**understand the consequences of the zero-suppression threshold the Monte Carlo should be tuned to **
**observed calorimeter energy and multiplicity distributions.  Simulated data and collider data should be **
**used to optimize the reconstruction and properties of physics objects as a function of threshold.  **
**Selection of the threshold will also require an understanding of the L3 processing time and the data**
**set size at L3 and off-line all as a function of threshold.**
**Specifically, the task force should:**
**Characterize the calorimeter performance on the cell level.**
**Characterize particle identification (such as energy response and resolution) as a function of threshold.**
**Tune the Monte-Carlo to the data at the cell and physics object levels.**
**Understand the consequences of the threshold level on L3 computing and data size and offline data size.**
**Recommend a zero-suppression threshold.**
**The task force will report to the spokespersons.  A preliminary recommendation should be available by October**
**15th and a final report by January 15, 2003.**

## Backups

## Pedestal rms vs Preamp cap. 

**Rama Calaga**

## Scalar ET

**Scalar ET**

**Gregorio Bernardi**

**450 MeV cell threshold**

**100 MeV cell threshold**

**1.5 ******** **

**2.5 ******** **