# Presentation: 476612

## Summary of HLT Studies by the Jet/MET Physics Group

**Shuichi Kunori**
**U. of Maryland**
**21-July-2000**
**Group Leader: Sarah Eno http://home.fnal.gov/~sceno/jpg/Default.html**

## Milestone and Tasks

**July’00 Milestone:**
**Demonstrate that data coming from Level-1 trigger can be reduced by a factor of ~10 using calorimeter information.**
**Tasks**
**Software tools**
- Verify ORCA4
- Create ntuple-files
**Understand offline performance for jet/met/tau at 10E34.**
**Develop algorithms for Level 2 (and implement in ORCA).**

**(shown on June 6th.)**

## HLT algorithm

**Jets**
**Improve Et resolution and Et scale**** **
**improved jet axis with finer granularity (1x1 instead of 4x4 towers)**
**LSB: L1(Et=0.5~1.0GeV) -> L2(Et=0.2GeV)**
**energy calibration (non-linearity, pile-up energy)**
**Reduce low Et fake jets due to min-bias pile-up**
**jet shape & smaller window size**
**MET**
**Improve resolution**
**energy calibration (non-linearity)**
**Tau**
**improve shape cuts at L2**
**use tracker information for isolated charged tracks at L3.**

## Software Tools

**The software chain finally established.**
**CMSIM- no known bug**
- To be updated before next production.
**new eta-phi segmentation - cannot mix with 116 data.**
**ORCA4- big improvement**
- Random mixing of min-bias events.
**full pile-up activated - very critical for Jets & MET studies.**
- Re-organization of Calorimeter code
**clean software - good start for future, but required large effort to re-establish the software chain.**
**Ntupel Maker - working!**
- Standard ntuple files
**been shared by many members.**
- For Jets/MET only
**need to establish common ntuple files for all groups.**

## Monte Carlo Samples

**Large data set.**
**100k min-bias events**
**600k QCD events (10-470GeV)**
**~ 10 sets of signal sample**
**+ single particle samples for verification.**
- Thank for good production team and system.
**Need planning for next step**
**event filter at particle level before cmsim**
**an extended list of signal/background samples**
**production with different parameters for special studies, e.g. study of front end electronics.**
**Even larger event sample, e.g. 0.5~1.0E6 of min-bias events for pile-up.**

## Tau Trigger

**- New L1 Tau trigger has been**
**   ****introduced since Nov’99.**
** **
**   ****- a big improvement (29%->64%)**
**     ****for the low mass Higgs **
**     ****(200GeV) ****(#)**
**   ****- High mass Higgs may be**
**     ****triggered by L1 jet trigger.**

**(#) gg->bbA/H, A/H->2********->h++h-+X**
**off-line cuts: Et(********-jet)>60GeV**
**     ****| eta(********-jet)|<2.4, 1 prong ********’s.**

**L1**

## Tau Trigger

**L2 Tau trigger operates on **
**the 1st L1 tau.**
**    ****1) reconstruct a jet**
**    ****2) calculate e.m. isolation**
**           **
**       ****P(isol) = **
**       ****Et****ecal****(R<0.4) - Et****ecal****(R<0.13)**
**    **
**   ****3) accept event if P(isol) < Pcut.**

**L2**

**(efficiency for t’s passed L1)**

**New isolation cut provides**
**constant efficiency over large**
**Et region.**

## L2 Tau Trigger

**L3: **
**Use tracker information**

**L2:**
** ****reduction = 10 at 65% eff.**
**     ****4kHz -> 400Hz**

## Jet Trigger

**Problems to solve:**
**   ****- large QCD jet rate**
**   ****- pile-up at E34**
**       ****- signal pulse spread over**
**         ****multiple beam crossings.**
**   ****- non-linear response of**
**     ****calorimeter**
**        ****- Et-eta dependent**
**   ****- difficult to trigger low Et jets**
**New 12x12 sliding algorithm **
**has been introduced in L1**
**since Nov.99.**** **

**Eta-Et dependent correction**
** ****Et(corr)= a0 + a1 * Et(obs)**

## Jets

**Jet Energy resolution before/after correction**

**- Simple energy correction**
**  ****improves overall resolution.**
**- Next step:**
**    ****- apply this to L1/L2.**

## Low Et Jet Trigger

**Problems to solve:**
**  ****- large effect by pile-up.**
**       ****<17GeV> in R<0.6**
**       ****due to min-bias**
**       ****events at E34.**
**         ****-> Fake jets**
**  ****- Sensitive to threshold**
**    ****cuts.  **

**Rate(12x12)/Rate(6x6) = 2.1**
**for 40GeV for pile-up events.**

**12x12 window vs 6x6 window**

**Smaller cone/window pick**
**less pile-up energy, **
**(I.e. less fake jets)**

**(0.5 GeV threshold)**

## Low Et Jets: ResolutionDependence on window size and threshold

**Thres.**
**0.0 GeV**

**1.0 GeV**

**0.5GeV)**

**Better resolution**
**   ****- larger window**
**   ****- lower threshold**

**Next step:                                on**
**  ****- apply smaller window          ****low Et QCD multijet sample**
**  ****- apply some shape cut         ****qqH**
**  ****- energy correction                 ****WH**

**Low Et Jets: Resolution****Dependence on window size and threshold**

**12x12**

**6x6**

**(35GeV < Et(genjet) < 45 GeV)**

## MET Trigger

**Problems to solve:**
**  ****- Long tail due to pile-up**
**     ****- sensitive to pedestal**
**        ****& pile-up energy**
**        ****subtraction**
**     ****- depend on threshold**
**  ****- Energy scale**
**  ****- Sensitive to noise**
**  ****- Sensitive to dead channels**

**5kHz at MET=80 GeV**

**L2/Offline MET**

**(L1 rate ~ 8~10kHz)**

## MET Trigger

**L2/offline MET**

**Contribution from QCD Jets**

**Next:**
**  ****- Calculate L1/L2 rates**
**  ****- Efficiency curves for**
**    ****various signal channel.**
**  ****- Understand offline**
**    ****performance.**

**How can we reduce**
**and control the rates?**
**  ****- optimize threshold**
**         ****higher threshold**
**          ****= less pile-up &**
**             ****worse resolution**
**  ****- energy calibration**
**  ****- combine with jets/leptons**
**            ****~50 reduction with **
**             ****jet > 80GeV (???)**

## Plans for July Milestone

**1) redo L1 rates ****- done for tau and MET**
**2) construct maps for eta-Et dependent jet energy correction **
**    ****for offline (L2) and L1 ****- done (almost)**
**3) do L1/L2 jet rates with jet energy correction**
**4) see effect of jet energy correction on offline MET **
**5) do L2 MET rates with jet energy correction, if 4) works.**
**6) calculate L2 tau rejection rate with new L1 tau trigger. ****- done**
**7) support e+jets by the egamma group**
**8) start developing a common ntuple for jets/met/tau,**
**    ****electrons/gamma and muons. **

**(as of June 6th)**

## After July Milestone

**1) tracker information for L3 tau trigger.**
**2) proper HCAL electronics simulation.**
**         ****(pulse shape, time jitter etc.)**
**3) optimize offline MET calculation**
**4) optimize handling of low Et jets (Et<40GeV)**
**5) improve jet energy calibration and pile-up**
**    ****energy subtraction**
**6) migrate to a common ntuple.**
**7) production with new cmsim (updated geometry,**
**    ****larger HF shower library, etc.)**

**(plan as of June 6th)**

**(+ pixel for jets ?)**

**(+pedestal subtraction)**

## Conclusion

**Software Tools**
**“****cmsim - orca4 - ntuplemaker” finally working!  ****(almost)**
**L2 Tau**
**Isolation cut provided a factor of 10 reduction over L1 with efficiency ~65%.**
**Next - use tracker at L3****.**
**Jets / MET**
**Analysis of ORCA4 data just started.**
**Follow the plan shown on June 6th.**
- Many parameters and algorithms to test.
**Threshold, LSB, pedestal&pile-up energy subtraction, cone & window sizes, energy calibration, use of tracker/pixel etc.**
**L****ow Et Trigger and MET trigger are real challenge at 10E34, Hope to contribute to triggers on low mass scale physics.**