# Presentation: 821982

## HCAL--JET/METStatus and Plans

- S.Eno/S.Kunori, U. Maryland
- For the HCAL-Jet/MET group

- Salavat Abdullin, Sylvia Arcelli, Sunanda Banerjee, Sudeshna Banerjee, James Branson, Jim Brooke, Pamela Chumney, Jordan Damgov, Sridhara Dasu, Isa Dumanoglu, Sarah Eno, Dan Green, Pal Hidas, R. Kinnunen, V. Konoplianikov, Andrei Krokhotine,Olga Kodolova,Vladimir Kolosov,Victor Kolosov, Shuichi Kunori, Kajari Mazumdar, Alexandre Nikitenko, Alexei Oulianov, Wesley Smith, Eliane Trepagnier, A. Urkinbaev, Irina Vardanyan , Hans-Peter Wellisch

**Notes:**
So, I’m going to tell you about the results from the jet/met group

## Outline

- For the DAQ TDR
-  develop fast, robust, highly efficient algorithms for reconstruction of jets and MET for the HLT
-  Calculate rates for jet and MET HLT triggers
-  develop trigger strategy for SUSY to jets+MET, Invisible Higgs, and dijet resonances
-  understand the sizes and bandwidth needs of the HCAL calibration samples
-  verified that the HCAL data size is reasonable in view of the DAQ bandwidth
- In preparation for the Physics TDR
-  develop algorithms for the reconstruction of jets and MET that optimize resolution
-  develop and certify a GEANT4-based simulation of the HCAL within OSCAR

**Notes:**
So we’ve been working on the same kind of things the other groups have
For the DAQ TDR, we’ve
Susy in the jets and missing ET channel

## HLT Jet Algorithm

**HLT Jet Algorithm**

- These trigger studies use a simple cone algorithm, with no splitting/merging  appropriate for HLT since fast

- Cone size 0.5, seed threshold 2 GeV, minimum jet ET 10 GeV
- Optimized at high luminosity for resolution and fake jet rejection

**Notes:**
We use a cone size of 0.5 because it gives slightly better resolution at high luminosity, but these results have a negligible dependence on the cone size.  The seed threshold and minimum jet ET are set as high as possible while still maintaining 100% efficiency.  We set them high in order to reduce fake jets from pileup interactions and noise.

## Jet Calibration

**Jet Calibration**

- Calibrate both Level-1 and HLT jets (shown for low lum)

- e/ goes as E, not ET.  Physics goes at ET.  Plus, Different technologies

**Notes:**
After the jets are reconstructed, they have to be corrected for the nonlinearity of our calorimeter.  Our calorimeter is nonlinear and thus its response depends on the energy of the jet.  At a fixed ET, jets in the forward calorimeter have a much larger E, so the response depends on eta. These plots here show the ratio of the Et’s of the reconstructed jets to the generator level ones versus ET and eta.  The response is large at larger ET and larger eta for the uncorrected jets, and is flat for the corrected jets.
When we take real data, we will use photon plus jet data to do this calibration.  

## Jet Resolutions

- HLT jet resolution at low and high luminosity

**Notes:**
These plots show the jet energy resolutions as a function of ET both before and after calibration and for high and low luminosity  The resolution is somewhat worse at high luminosity as expected.  The calibration gives a slight improvement to the resolution.  However, the main effect is to reduce the eta dependence of the trigger efficiency.  The resolution determines how low you have to cut on reconstructed ET in order to be  efficient for a generator-level jet of a given ET. 

## Jet Rates

- Insensitive to details of the simulation

- Low Lum

- High lum

**Notes:**
The jet rates don’t depend a lot on the details of our simulation, which is nice.  Here you see the rate for a single jet trigger as a function of ET for 

## Jet Rates: Low Lum

**Jet Rates: Low Lum**

- 1 kHz at Level-1: 180 GeV (1 jet), 95 GeV (3 jet), 80 GeV (4 jet)
- 1 Hz at HLT: 660 GeV (1 jet), 250 GeV (3 jet), 150 GeV (4 jet)

- Rates very similar at L1 and HLT

**L1**

**HLT**

**Notes:**
So, here are the rates for our jet triggers, both for L1 and HLT at low luminosity.  The rates are very similar at L1 and for the HLT.  The spread between the rate versus generated raw is a bit smaller for offline due to the better resolution.

## Jet Rates: High Lum

**Jet Rates: High Lum**

- 1 kHz at Level-1: 250 GeV (1 jet), 125 GeV (3 jet), 110 GeV (4 jet)
- 1 Hz at HLT: 865 GeV (1 jet), 330 GeV (3 jet), 200 GeV (4 jet)

- Rates very similar at L1 and HLT

**L1**

**HLT**

**Notes:**
Here are the rates at high lum.  For the single jet triggers, they are basically just 5x the low lum rates.  For the 4 jet triggers, the rate is a bit higher due to jets from the pileup interactions.

## HLT MET Algorithm

- Tried 3 algorithms:
-  simple sum over towers
-  using jets with jet energy scale corrections and unclustered towers (“type-I”)
-  using jets with jet energy scale corrections and unclustered towers corrected using the jet energy scale correction for a 30 GeV jet (“type-II”)
- Simplest works as well as others at trigger level (“type II” works better in some offline analyses)

## MET calibration and resolution

**MET calibration and resolution**

- Low luminosity SUSY events

- Mean and RMS of the difference between generator and HLT MET for 3 different HLT MET algorithms

**Notes:**
This plot shows the mean and the rms of the difference between the generator and the HLT met for the 3 algorithms for some SUSY events.  As you can see, adding the jet energy scale corrections does improve the met energy scale, but it doesn’t improve the resolution.

## Met Rates

- Very sensitive to details of the simulation (and a great way to find bugs in the calorimeter simulation )

- Raw rates are very difficult to interpret because of the large and algorithm-dependent difference between HLT and generator MET

**Sensitive to hardware problem.**
**Need good monitoring and quick**
**    ****cure.**

**Notes:**
Here are the rates. The red and blue curves show the rates at the generator level at low and high lum.  Below 60 GeV, the MET comes from particles that go down the beam pile.  Above 60 geV, the MET is mostly from heavy flavor decays.  The black and green curves show the reconstructed MET at low and high lu.  As you can see, much of the MET comes from the energy resoluition of the calorimeter, and only at very high et does the reconstructed rate approach the generator rate.  This means that the MET rates are very senstivie to the details of the simulation, and we’ve found several very rare bugs while doing this study.

## Additional Dijet suppression

**Additional Dijet suppression**

- Only useful for large MET

**Notes:**
Most of our background comes from dijet events, when one of the jets is mis-measured.  We’ve looked to see if we could further supress this background by seeing if the MET is aligned along a jet.  We found this kind of cut inefficient for SUSY because the MET  tends to be along a jet in these events too.  We did find we could get some rejection by requiring the two leading jets not be back to back.  This plot shows the rate with and without this cut.  It is of some use when the missing ET is large.

## SUSY: Intro

- Considered MSUGRA with and without R-parity violation
- With:  substantial MET due to stable
- Without: difficult signature... events  with many jets.  Some MET due to W, heavy flavor, etc in decays
- Points chosen to give a variety of signatures

- Which one has the R-parity violation???

**Notes:**
The first physics process we considered is susy in the jets+met channel.

## SUSY: Intro

- Optimized sum of efficiencies for a fixed rate to tape

- Low lum: points near Tevatron reach
- Used for low lum optimization
- High lum: points near LHC reach
- Used for high lum optimization

- MSUGRA with A0=0, tan()=10, and >0

**Notes:**
These show the exact msugra parameters we used.  These points here were chosen at the TeVatron reach and are used for the low luminosity optiization.  These points here are at the LHC reach, and are used for the high luminosity optimization.  Its hard to know how to optimize a trigger table for SUSY, because we don’ t know in advance what it will be like..  So, we optimized the sum of the efficiencies of these points for a fixed rates to tape.

## SUSY: Low Lum Level 1

- not hard...
- With just two triggers
- 1 jet > 130 GeV
- 3 jets > 60 GeV
- We can have efficiencies of .89,.90,.81,.94,.95,.88 for points 4,5,6,4R,4R,6R (total efficiency, not with respect to offline cuts) and a rate to tape of 2 kHz.
- Add more triggers and can get a little more.

**Notes:**
Triggering on SUSY at level 1 at low luminosity is not hard.  These events contain hard jets.  This plot shows the et of the leading and second jet from point 4, though the points all look similar.  With just two triggers...

## SUSY: Low Lum HLT

- harder...

-  MET>170
-  3 jets > 60 and MET> 110
-  4 jets > 120
-  1 jet > 190, MET>90, and (j1,j2)>0.5
-  2 jets>40, MET>100, and (j1,j2)>0.5
-  4 jets>80, MET>60, and (j1,j2)>0.5
- gives efficiencies of 0.78, 0.74, 0.54, 0.38, 0.27, 0.17 for points 4,5,6,4R,5R,6R and a rate to tape of 3 Hz.
- Some of these are triggers with very steep rate curves (4 jet)

**Notes:**
It’s a little harder to get very high effiencies in the HLT with just 3 Hz to tape.  We need several triggers.  But, we get good efficiencies for the r-parity conserviing points.  The R-parity violating points are harder.  For one point the efficiency is just 17%.  However, this is the absolute efficiency, not the efficiency with respect to the offline cuts, so its not clear we could use the events we are throwing away anyway.

## SUSY: High Lum

_**Level 1**_   1jet>90&<MET>80      3jets>90
-                 .90,.98,.92,1.0,1.0,.99  for 2 kHz

- almost too easy...

_**HLT**_      MET> 170           4jets>150
-                .95,.94,.83,.90,.89,.65 for 3 Hz to tape

**Notes:**
The high mass susy points are trivial to trigger on, even at high luminsotiy.  When you have 1000 GeV jets, you can trigger.

## Invisible Higgs

- Level 1: 1 jet>60, MET>65 Low Lum (e=0.98) , >70,112 High Lum (e=0.79)

**Working on other trigger strategies for high lum (M cut, ******** cut with prescaled background trigger without the ******** cut)**

- Low lum: easy to get e>.95 for 0.1 Hz to tape
- High lum:  e=0.6 for 0.1 Hz to tape

**Notes:**
Another new particle we considered is an “invisible” higgs.  This is a higgs that decays to a pair of  SUSY LSPs and thus produced no signal in the detector.  We can look for it, though, by looking for the associated tag jets that are there when this higgs is produced via vector boson fusion.  The signature is two jets with a large rapidity gap and MET.  The lower the mass, the harder it is to trigger on, so we set the mass just above the LEP reach.  For low luminosity, we found a trigger with an efficiency of 98% with respect to the offline cuts and a rate to tape of 0.1 Hz.  For high luminosity, it is harder to keep the rate at 0.1 Hz.  Our current best trigger, which requires a jet with ET> 40 GeV, a rapidity gap betwee the leading 2 jets of 4.4,  the two leading jets in opposite halves of the detector, and MET> 160 GeV has an efficiency for events that pass the offline cuts of 60%.  We are still working on improving this trigger.

## Dijet Resonances

**Dijet Resonances**

- Limits from Tevatron
- W’               720 –920 GeV
- Z’                 720 –940 GeV
- E6 diquark   570 –780 GeV
- Axigluon     1160 –1300 GeV
- q*                910 –1180 GeV

- Unprescaled 1 jet trigger is 660 GeV (x2mass of 1320 GeV)

**Notes:**
We also have started to think about the data samples and triggers we would need to look for dijet resonances.  Our unprescaled 1 jet trigger will be efficient only starting around 1400 GeV, but many of the tevatron limits on these particles will be substantially lower.  Finding these low mass resonances will be tricky, because of the very large background. At this point, we have only conisdered how much data we would need to have a statistically significant signal in a big around the mass.   At the tevatron, they fit the spectra to an ansantz function + a signal shape.  There will be systematics errors associated with the ansatz function, probably large ones, that we have not considered yet, and may even make this kind of search impossible.  But...

## Dijet Resonances

- Time to have a statistically significant (5) number of Z’’s in a window around the mass for a constant 20 Hz to tape

- unprescaled

- Blue: dynamic prescale
- Red: fixed prescale

**Notes:**
If you just want to know how long you need to run to get a statistically significant sample, here’s a plot.  This is for a constant 20 Hz to tape and a trigger threshold at M/4, the x axis is the mass, the y axis is the time til discovery for a fixed prescale and for a dynamic prescale that decreases as the luminosity decays away.  We are continuing work on this subject.

## CPU Analysis

- Time is small (budget is 300 ms/event)
- Similar for physics and for backgrounds
- Tower building dominates at low luminosity
- Tower building and jet reconstruction about equal at high luminosity

**Notes:**
So, that’s our work on rates and trigger tables.  We’ve also checked to see if our algorithms are fast enough for the HLT, and they are.

## Calibration: General

- Relative calibration of scintillator tiles:
-  during construction: collimated gamma source
-  track changes during running: movable gamma source tubes
-  track changes during running: minimum bias data
- Linearity of electronics and timing
-  UV laser and blue LED’s
- HCAL Energy scale
-  test beam data:  source data - ADC - GeV
-  single particle (QCD events, tau trigger)
- Jet Energy Scale
-  **** + jet data, Z+jet data, di-jet data
-  W->jet data (in ttbar events)

## HLT for calibration:  + jet

**Several processes will be used for calibration of jet energy. Among**
**those considered so far (e.g. Z+jet, ttbar etc.), only ********+j requires**
**a dedicated HLT.**

****** ****+ jet  trigger****    **
** ****For ET>80GeV:**
**     ****- HLT single photon **
** ****For ET<80GeV**
**     ****- L1 e/gamma  (ET>23GeV)**
**     ****- very tight ******** isolation  **
**       ****with pixel and ECAL**
**     ****- pre-scale**** **

**E****T****(********)**

**100**

**1000**

**1%**

**.1%**

**.01%**

**Statistical error after 3mo. **
**running with 1Hz at 2E33**

## -symmetry calibrationwith min-bias events

******-symmetry calibration****with min-bias events**

**(****1.4 hours****)**

**( 5.6 hours)**

- eta

- Accuracy (%)

**Process min-bias events in the HLT farm at 1kHz**
**and send “histograms” to tape. **

## Energy Flow for Jets

**Energy Flow for Jets**

- Improves energy scale!

- Improves resolution!

- Use tracking information to improve jet reconstruction
- Used at LEP and CDF

**Notes:**
We’ve also started our work on algorithms for jets and MET for the physics TDR. For jets, we’ve been working on improving the jet energy resolution by using the tracker instead of the calorimeter whenever possible.  

## toward Physics TDR

## GEANT4

**GEANT4**

- Done...
-  HCAL geometry and hits are in OSCAR
-  GEANT4 hadron shower generation verified to be as good as GEANT3 at describing our 1996 test beam data
- To Do...
-  HCAL needs to be integrated into new OCAR framework for geometry,hits, user inferface
-  shower library for HF needs to be integrated
-  more testing/comparisions for single particles, jet, MET between CMSIM/OSCAR
-  compare to 2002 test beam

- Physics TDR will use OSCAR/GEANT4.  Important that this be ready and well tested

## Summary

- have
-  satisfactory algorithms for reconstructing jets and MET in HLT
-  calculated rates for jets and MET at low and high luminosity
-  checked our bandwidth and CPU requirements are in budget
-  designed satisfactory trigger tables for SUSY, dijet resonances, and invisible Higgs
-  checked the bandwidth needed for calibration samples is reasonable
-  started promising work on algorithms to use offline (for physics TDR)
-  exercised our software and production facilities
-  written our portion of the DAQ TDR

- THANKS TO ALL THE PARTICIPANTS IN THE HCAL--JET/MET GROUP!!!