Presentation on theme: "H/Abb -> 4b’s process & Multi-Et-Threshold Study for 4jet Trigger Kohei Yorita Young-Kee Kim University of the FTK Meeting on July 13 th, 2006."— Presentation transcript:
H/Abb -> 4b’s process & Multi-Et-Threshold Study for 4jet Trigger Kohei Yorita Young-Kee Kim University of the FTK Meeting on July 13 th, 2006
2 4jets w/o btag LVL1 Out 1KHz LVL2 Out 100Hz 4 Jet Trigger Review LVL1 (10us)LVL2 (20ms) Current Menu (w/o FTK) 4J(~60) : 200Hz4J(70) : 100Hz w/ FTK4J(40) : 1KHz4J(40) : 100Hz w/ btag 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 !!! LVL1 Out 200 Hz
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) M A (GeV ) No Pt cut Pt > Correct oneShown at last FTK meeting Xsec used was without parton Pt cut ! But MC was generated with Pt > 10 GeV !!! Cross section BR (pb) Still impressive Improvements !!!
5 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), 1 st and 2 nd jets are more energetic jets (from H/A) 3 rd and 4 th jets Et spectra are much softer. Questions are, Keeping LVL1 output rate, How much 4 th (and 3 rd ) jet Et threshold can be lowered by increasing 1 st and 2 nd jet ? How much it helps signal acceptance ? What’s physics impact ? Multi-Threshold Study
6 MC Samples 851 ev passed 55 ev passed 5 M events Cross sections yt>25 : 0.36 mb yt>20 : 0.83 mb yt>10 : 9.8 mb 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 4 th Pt > 20 !!!) Default is Sherpa 2to2+2to3 with yt>25 sample. But nice to lower yt cut for multi-threshold study.
7 Multi-Threshold Scan Procedure 4 th jet Pt > 30 GeV 1 st jet Pt : … > As already discussed, interesting region to be compared with single value threshold is ~ 1KHz (Max LVL1 output (4J40)). Case Category (for jet pt order) Case1: j1>j2>j3>j4 : 4 parameters (no physics bias) Case2: j1>j2>j3=j4 : Good for hard 2j + soft 2j Case3: j1>j2=j3>j4 : any physics model ? Case4: j1=j2>j3>j4 : If back-to-back two jets + X ? Case5: j1>j2=j3=j4 : If only 1 st jet is really energetic Case6: j1=j2=j3>j4 : Good for 3jets + X process Case7: j1=j2>j3=j4 : Good for hard 2j + soft 2j Case8: j1=j2=j3=j4 : Single Threshold 4 th jet Pt threshold is set to be 20 GeV or 30 GeV, and 2 nd, 3 rd and 4 th jet Pt are changed up to 100 GeV by 10 GeV step. (see figure. In each range, 2 nd and 3 rd jet Pt are scanned from 30 GeV to 1 st jet Pt.) 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 Cut valueTrig RateS(500)Cut valueTrig RateS(500) Default (w/o FTK) Hz6.3 % Hz6.3 % Default (w/FTK) Hz24.2 % Hz24.2 % 4 th Jet Pt > 20 GeV4 th Jet Pt > 30 GeV Case1: j1>j2>j3>j Hz37.3 % Hz33.3 % Case2: j1>j2>j3=j Hz45.1 % Hz34.6 % Case3: j1>j2=j3>j Hz37.3 % Hz30.5 % Case4: j1=j2>j3>j Hz41.3 % Hz33.0 % Case5: j1>j2=j3=j Hz45.9 % Hz34.7 % Case6: j1=j2=j3>j Hz31.5 % Hz30.6 % Case7: j1=j2>j3=j Hz45.3 % Hz34.5 % Case8: j1=j2=j3=j KHz54.3 % KHz36.5 % Each point was selected when trigger rate became closest to 1KHz in each case. Keeping 1KHz by increasing 1 st (~80 GeV), 2 nd (60-70 GeV), and 3 rd (40-50) jet Pt but by lowering 4 th jet Pt (20, 30 GeV), Signal (M_A = 500 GeV) acceptance increases by a factor of 1.5~2 !!! Numbers in red are just highest 3 in each column.
9 With Other Mass Samples 4 th jet Pt > 20 GeV 4 th : 20 GeV Sig eff(200)Sig eff(300)Sig eff(400)Sig eff(500)Sig eff(900) Default (w/o FTK)0.6 %1.7 %3.7 %6.3 %17.3 % Default (w/FTK)5.0 %11.3 %18.1 %24.2 %39.4 % Case1: %17.1 %28.4 %37.3 %55.3 % Case2: %17.7 %33.5 %45.1 %63.8 % Case3: %16.9 %28.4 %37.3 %55.3 % Case4: %17.9 %31.3 %41.3 %59.4 % Case5: %17.8 %34.5 %45.9 %64.0 % Case6: %13.8 %23.3 %31.5 %50.4 % Case7: %18.1 %33.4 %45.3 %63.8 % Case8: %39.8 %48.3 %54.3 %66.0 % > 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 1 st and 2 nd leading jets are not so hard. Numbers in red are just highest 3 in each column.
10 With Other Mass Samples 4 th jet Pt > 30 GeV 4 th : 30 GeV Sig eff(200)Sig eff(300)Sig eff(400)Sig eff(500)Sig eff(900) Default (w/o FTK)0.6 %1.7 %3.7 %6.3 %17.3 % Default (w/FTK)5.0 %11.3 %18.1 %24.2 %39.4 % Case1: %15.6 %25.6 %33.3 %49.6 % Case2: %16.2 %26.7 %34.6 %50.7 % Case3: %14.7 %23.4 %30.5 %47.0 % Case4: %15.1 %25.0 %33.0 %49.5 % Case5: %16.5 %26.9 %34.7 %50.7 % Case6: %14.7 %23.4 %30.6 %47.1 % Case7: %16.2 %26.5 %34.5 %50.6 % Case8: %21.5 %30.0 %36.5 %51.1 % > 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 ?? Numbers in red are just highest 3 in each column.
11 Summary & Plan Multi-Threshold with 4 th 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 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 !!