# Presentation: 850460

## Results on Jetsfor HLT Studies by the Jet/MET Physics Group

**Shuichi Kunori**
**&**
**Silvia Arcelli**
**U. of Maryland**
**21-July-2000**

## HLT Jets Algorithm

**L2**
**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**
**Combine with leptons and MET**
**cuts on correlation, e.g. delta-eta, delta-phi...**
**L3**
**b-tagging**

## QCD Jet Rates

**Very High rate!**
**  ****1 kHz = acceptable L1 rate for jets**
**1 jet    165 GeV**
**2 jets  120 GeV**
**3 jets    75 GeV**
**4 jets    55GeV**
**Trigger Output (max):**
**L1  75 kHz**
- (3 kHz for Jets)
**L2  1 kHz**
**L3  100 Hz (to tape)**
**How to stay below 100 Hz ?**
**Guideline: 20Hz for Jets, MET, combination.**

**(S.Dasu)**

## L1 Single Jet Rates

**Shown on Nov.4’99**

**- Threshold @ 1KHz**
**  ****old 4x4       340GeV**
**  ****12x12          250GeV**

**1 kHz**

**12x12 for high Et jet**
**             ****OK!**

## Low Et Physics

**Low Et Jets + others**
**(by V.Gavrilov)**

**Et (jet) Threshold**
**25 GeV**

**Need estimation of**
**physics rates.**

## qqH(135)

**Need to study both!**

**qqH (135GeV)**
**      ****-> tau -> e/mu +X**
**      ****-> tau -> jet + X’**

**Possible L1:**
**   ****e(22) + 1 jet(90?)**
**   ****e(22) + 3 jets (30)**

**and also to cover decay modes as many as possible!**

**>> Study done by S.Lehti(HIP),S.Ilyin(MSU), A.Nikitenko(HIP) <<**

## Eta Coverage

**=> Need to cover both HE and HF region.**

**(A.Nikitenko)**

## 1 lepton + 3 jets

**=> 3 jets (>30GeV)**

**=>Lepton (>15GeV)**

**(A.Nikitenko)**

## Low Et Jets and Pile-up

**Reco with pile-up**

**Reco w/o pile-up**

**Generated**

**Fake jets < 40GeV**

**(R<0.7)**

**(A.Krokhotine)**

**ORCA3 in-time**
**pile-up only**
**(no Et correction****)**

## ECAL+HCALNon-linear response

**‘****96 H2 Test Baem Data**
**         ****single pion**

**   ****ORCA3**
**3GeV Pions**** **

**0**

**100**

**200**

**300  **
**      ****(GeV)**

**1.5**

**3.0**

**5.0**

**0**

**eta**

## Jet Energy Correction

**Et-eta dependent correction for QCD jets**

**ORCA3**

**no pile-up**

**In-time pile-up**

**E(corr) = a0 + a1 * Et(obs)**

**Corrected scale flat within 1 - 3%**

## Jets ResolutionBefore/after energy correction

**(Average over eta range < 3.0)**

**No pile-up**

**In-time pile-up**

**3-8% improvement!**

**(ORCA3)**

## Jet Energy Correction(no pile-up)

**L1**

**L2**

**Corrected scale flat within a few percent****.**

**ORCA4**

## Jet Energy Correction(full pile-up)

**L1**

**L2**

**same as no pile-up case**

**weak eta dependence**

## Jets Resolution(before/after correction)

**L1**

**L2**

**Improvement**

**Not much improvement!**

**(Correction) =( linearity) + (pile-up energy)**
**Can we improve, if we separate those two?**

## L2 Jets Rateswithout Et correction

**First rate calculation,  < 24 hours old.**** **

**In progress: L1/L2 rates at 95% point.    Then: Et corrected.**

**By S.Abdoulline**

## Conclusion

**We are trying to improve Jet energy resolution at L1/L2 in order to ger sharper turn-on in efficiency curves.**
**We have created  first version of a set of eta-Et dependent correction functions for L1/ L2 jets.**
**We will apply the corrections to L1/L2 and calculate rates.**
**We continue to look for  improvement of Et correction.**
**Other activities in progress:**
**Suppression of  fake jets using smaller window/cone and shape cuts.   (see next talk).**
**Improvement of  pile-up energy subtraction.**
**Use of j-j, j-met, j-l correlation at L1/L2**
**Beyond:   ****use of tracker(pixel) & .....**