# Presentation: 563733

## Jet Energy Reconstructionwith the CMS detector

**Shuichi Kunori**
**U. of Maryland**
**27-March-2002**
**(for the CMS collaboration)**

**10****th**** International Conference on Calorimetry**
**In High Energy Physics**** **

## Outline of talk

** ****Calorimeter response to single pion **
** ****Jet energy corrections**
**       ****simple correction with mapping**
**       ****using tracks**
** ****Extensions to MET (missing E****T****)**
** ****Conclusions**

**Many Thanks to my CMS colleagues, especially**
**     ****S.Abudullin, S.Arcelli, V.Drollinger, S.Eno, D.Green, O.Kodolova   **
**     ****A.Krokhotine, A.Nikitenko, A.Oulianov, I.Vardanyan**

## CMS Detector

**Tracker**
**    ****All silicon**
**    ****|********|<2.4**
**ECAL**
**    ****PbWO4 crystals**
**    ****e/h ~ 1.60**
**    ****|********|<3.0**
**HCAL (barrel/endcap)**
**   ****Scint-tile & brass**
**                 ****sampling**
**   ****e/h ~ 1.39**
**   ****|********|<3.0**
**   ****– ****4 Tesla field –**
**HCAL (fwd)**
**   ****Quartz-fiber & iron**
**   ****3.0<|********|<5.0**

## Pion Response: Linearity

**96’H2 Teast Beam Data**

**CMS Simulation**

**ECAHL+HCAL: Non compensating calorimeter**

## Simple Jet Energy Correction (#1)

**Map of response in E****T****-********:    E****T****(corr)=a + b x E****T****(raw) + c x E****T****(raw)****2**
**                                     ****a,b,c depends on E****T**** and ******

****** ****Level 1 trigger, HLT trigger, offline**

## Jet Energy Correction

**Jet Energy Correction**
- Correction for detector effects
**e.g. Calorimeter jet (cone R<0.5) ******** Particle level jet  (cone R<0.5)**
**( Not for physics effects, e.g. final state radiation etc. )**
**Algorithms:**
**Jet based**
- E = a x (EC+HC),       a depends on jet(ET,)
**     ****baseline:  implemented in both trigger & offline.**
- E = a x EC + b x HC,  a, b depend on jet(ET,)
**     ****Note: no longitudinal segmentation in ECAL (1.1********) and HCAL**
**Cluster based**
- 3)   E = em + had      (using calo only)
**     ****Calib. coefficients to em-cluster and had-cluster, separately.**
**Use of reconstructed tracks**
- 4)   E = E0 + (Tracks swept away by 4T field)
- E = EC(e/) + (EC+HC)(neutral.h) + Tracks(charged.h)

## Effect of 4 Tesla Filed

**Fraction of energy escape **
**from a jet cone (R=0.5) **
**in 4T field.**

**Radius of ECAL front ~ 1.3 meters**
**Charged particles  P****T**** < 0.8GeV  **
**      ******** ****Looper in barrel.**

## Correction to B-field effect (#4)

**Track reconstruction efficiency by**
**ORCA (CMS reconstruction program)**

**Improvement of resolution**

**Add energy of charged tracks swept away**
**from jet cone (R=0.5) by 4T field.**

## Correction using Tracks (#5)”energy flow”

**E(corr) = E(calo) + ********E(out-of-cone tracks) + ********E (in-cone tracks)**
**                                                 ****corr. for 4T field                         corr. for calo response**
**For each track inside jet cone:**
**    ****Form a cluster around track:  3x3 crystals + 3x3 HCAL    **
**                                                                   ****  ****in  ********x********:  (0.017x3)****2**** + (0.087x3)****2****              **
**    ****Track – Cluster match:     -******** < E****track****– E****cluster**** < 2************ **
**                                                                             ****where        ********/E=100%/sqrt(E) + 5%,****  **
**    ****if matching is- **
**        ****YES:  ********E(in-cone) = +E****track****- E****cluster **
**         ****NO:   ********E(in-cone) = +E****track****- R****AVE                   ******** photon-charged pion overlap**
**            ****R****AVE**** = (estimate of average ECAL & HCAL response to charged hadron)**
**                  ****1) Identify whether hadron interaction started in ECAL or HCAL**
**                      ****by checking energy in crystals.**
**                  ****2) estimate true energy deposit in ECAL and HCAL using average**
**                      ****longitudinal shower shape.**
**                  ****3) estimate ECAL and HCAL response, R****AVE ****   (see page 11)**
**                     **

## Track – Cluster Match

**matching condition:  -******** < E****track**** – E****cluste****r < 2******
**            ****where **
**               ********/E=100%/sqrt(E) + 5%**
**               ****Cluster = 3x3 crystals + 3x3 HCAL tower**

## Estimation of Calorimeter Response

|  | Particles interact in ECAL | Particles not interact in ECAL |
| --- | --- | --- |
| RECAL | ETrack*0.4/(e/)ECAL | EMIP |
| RHCAL | ETrack*0.6/(e/)HCAL | (ETrack-EMIP)/(e/)HCAL |

**(e/h)****ECAL****=1.60, (e/h)****HCAL****=1.39**

**1) Simple average**

**2) Library of response**
**                   ****GEANT3 simulation for pion interactions started in ECAL.**

**E****ECAL**

**E****HCAL**

## Using Tracks  (#5)Resolution & ET Scale

**Resolution    **
**  ****20GeV  24% ******** 14%**
**100GeV  12% ********  8%**

**E****T**** Scale**
****** ****< 2% in 20-120GeV**

**0**
**1**
**2**
**3**
**4**

**0:  no correction (calorimeter only)   1:  calo response - simple average     2:  calo response – library       **
**3:  full correction (library of response, track-cluster match, out-of-cone tracks)**
**4   out-of-cone tracks correction only**

## MET (Missing Transverse Energy)

**Corrections**
**     ****Type 1:   Jet corr. **
**     ****Type 2:   Jet corr. + out of cone corr.**

**Out of cone corr. uses weights**
**for jet(30GeV) corr****.**

**Extension of the simple jet energy correction (#1) to MET.**
**MET(corr) = MET(calo) + ********{********E****T****(jet corr)****IN****}+ ********E****T****(min-bias corr)****OUT**

## Corrected MET for SUSY

**Mean offset**

****

**An extension of the simple jet energy correction improves**
**also MET energy scale and resolution.**
**Next:  Extend “energy flow” algorithm to MET.**

**SUSY event:  multi jets + MET**

## Conclusions

**Various algorithms to improve jet energy scale and resolution have been tested for CMS.**
**Simple mapping of jet response in ********-E****T**** space will be used in Level 1 & HLT trigger, and offline.**
**Large improvement with correction using tracks. **
- Resolution       20GeV: 24%  14%
-                           100GeV: 12%  8%
- Energy scale     < 2%  in 20-120GeV
**Extensions of jet energy corrections to MET look promising.**
**Our next step is**
**Apply those corrections to various physics processes (with complicated event structure) and test its performance.**
**Do more detailed analysis and fine tuning.**
**Extend “energy flow” algorithm to MET.**