H/Abb -> 4b’s process & Multi-Et-Threshold Study for 4jet Trigger

1. H/Abb -> 4b’s process &Multi-Et-Threshold Study for4jet Trigger Kohei Yorita Young-Kee Kim University of Chicago @ the FTK Meeting on July 13th, 2006

2. 4 Jet Trigger Review • Current (TDR) Menu : • High threshold of 4J(60) at LVL1 has • been determined due to poor LVL2 • reduction w/o btagging. • Here L2 reduction ~ 2, so 200Hz is • necessary at LVL1 output. • With FTK, threshold can be lowered down to 40 from 60, giving 1KHz. * We just assume Max 4J LVL1output is 1KHz, not limited by LVL2 reduction but data transfer and 4J trigger budget. (Total LVL1 rate : ~ 50KHz) So to maximize performance, LVL2 reduction has to be more than a factor of 10 by only btagging w/ FTK !!! 4jets w/o btag LVL1 Out 1KHz LVL1 Out 200 Hz LVL2 Out 100Hz

3. LVL2 Reduction by btagging Since we haven’t had realistic btagging rate and fake rate, Right plot shows LVL2 reduction vs Ru(Rejection against non-b jet) where btagging efficiency is 50% with different Nbtag (1-4). In order to have a factor of 10, We need (1) If 1btag : fake rate < 10 % (2) If 2btag : fake rate < 33 % (3) If 3btag : fake rate < 50 % I guess that (1) can be achievable by FTK ! So again real limit on LVL1 threshold is not from FTK at LVL2 ! In principle by FTK btagging, we can change Pt threshold as low as possible because even if fake rate is high, we can increase N of btag.

4. Update (Single Et Threshold for 4J) Shown at last FTK meeting Correct one Xsec used was without parton Pt cut ! But MC was generated with Pt > 10 GeV !!! Still impressive Improvements !!! Cross section  BR (pb)

5. Multi-Threshold Study • So far, only “single Et threshold” has been used even for multijet • trigger, but in most physics process (at least this channel : • H/Abb->4b’s), • 1st and 2nd jets are more energetic jets (from H/A) • 3rd and 4th jets Et spectra are much softer. Questions are, • Keeping LVL1 output rate, How much 4th (and 3rd ) jet Et threshold can be lowered by increasing 1st and 2nd jet ? • How much it helps signal acceptance ? What’s physics impact ?

6. MC Samples Cross sections yt>25 : 0.36 mb yt>20 : 0.83 mb yt>10 : 9.8 mb Default is Sherpa 2to2+2to3 with yt>25 sample. But nice to lower yt cut for multi-threshold study. We did expect to see “higher rate” around Pt > 20 GeV with yt 10, but yt cut 10 gives lower rate than 20 and 25, which dose not make any sense. Need to be understood why this happens. - Still under investigation. Since yt 20 and 25 samples agree very well even in lower Pt region, I used yt>20 as a default for multi-threshold study. (But down to 4th Pt > 20 !!!) 5 M events 851 ev passed 55 ev passed

7. Multi-Threshold Scan Procedure 4th jet Pt threshold is set to be 20 GeV or 30 GeV, and 2nd, 3rd and 4th jet Pt are changed up to 100 GeV by 10 GeV step. (see figure. In each range, 2nd and 3rd jet Pt are scanned from 30 GeV to 1st jet Pt.) 4th jet Pt > 30 GeV > As already discussed, interesting region to be compared with single value threshold is ~ 1KHz (Max LVL1 output (4J40)). 1st jet Pt : ….. 60 70 80 90 100 Then for each case (1-8), the closest point to 1KHz is chosen. And compare Trigger rate and Signal acceptance.

8. Multi-Threshold Scan Results Each point was selected when trigger rate became closest to 1KHz in each case. Numbers in red are just highest 3 in each column. Keeping 1KHz by increasing 1st (~80 GeV), 2nd (60-70 GeV), and 3rd (40-50) jet Pt but by lowering 4th jet Pt (20 , 30 GeV), Signal (M_A = 500 GeV) acceptance increases by a factor of 1.5~2 !!!

9. With Other Mass Samples 4th jet Pt > 20 GeV Numbers in red are just highest 3 in each column. > Please note that “FTK w/ single value” already improves signal efficiency by a factor of 2~9 depending on mass. See first 2 lines. > “FTK+Multi-threshold” : Additional factor of 1.2~2 at trigger level. > Case2, 5, 7 look promising, as expected, in high mass range, but not the case for low mass (200 ,300), because 1st and 2nd leading jets are not so hard.

10. With Other Mass Samples4th jet Pt > 30 GeV Numbers in red are just highest 3 in each column. > Even if Pt>30 GeV, “FTK+Multi-threshold” gives additional factor of 1.2~1.5. > Need to look at LVL1 parameterization. > Even if LVL1 param is used, ROI reconstruction efficiency is enough for low Pt jet ? Where are we considering this effect ??

11. Summary & Plan • Multi-Threshold with 4th Pt > 20, 30 GeV shows improvement on signal acceptance by a factor of 1.2~2.0 w.r.t. w/ FTK condition. - So “FTK+Multi-Threshold” seems best way to go. -- FTK bagging @ LVL2 : Good for low Higgs mass. -- Multi-Threshold : Good for high Higgs mass. - But comparisons of w/ and w/o FTK by “single threshold” should be clearly done first in documentaion. • Things to do : - So far all study has been done Atlfast Pt base. -- Need to redo by LVL1 Parameterization. - Figure out / validate new Sherpa sample (Erik’s), clarify yt cut 10 issue. - Good to try to measure dijet (H/A) mass. - Final Check with other generator & full sim. - Documentation … -- Being Prepared (just started..not much done yet.) - 4Jet Trigger Rate with multi-threshold discussion - H/Abb physics case w/ and w/o FTK. Now let’s try to finish as quickly as possible !!

12. Optimized Cut Values (single threshold) w/ FTK starts from (40,40,40,40) w/o FTK starts from (70,70,70,70)