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Progress on H/Abb -> 4b’s channel for the FTK physics case ~ 4jets trigger w/ and w/o FTK ~

Progress on H/Abb -> 4b’s channel for the FTK physics case ~ 4jets trigger w/ and w/o FTK ~. Kohei Yorita Young-Kee Kim University of Chicago

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Progress on H/Abb -> 4b’s channel for the FTK physics case ~ 4jets trigger w/ and w/o FTK ~

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  1. Progress on H/Abb -> 4b’schannel for the FTK physics case~ 4jets trigger w/ and w/o FTK ~ Kohei Yorita Young-Kee Kim University of Chicago @ the FTK Meeting on May 2nd, 2006

  2. Trigger Rate Comparisons > Requiring 4jets with different Pt cuts. > Trigger Rate : Sherpa 2to3 > Sherpa 2to2 > Pythia > No bb production in Sherpa but gluon splitting produces b quarks. bb production : 0.48 mb with no pt cut ~ 0.002 mb with pt>20 GeV, < 1% w.r.t. dijet - Need more check. > Use Sherpa 2to3, yt>25 as a default - Better kinematics and conservative. 1 btag 2 btag 0 btag 3 btag 4 btag

  3. Atlfast Pt vs LVL1 8x8 Calo Et Old : |eta| < 2.8, JETB New : |eta| < 3.2, against both JET and JETB (option) > Slope became more closer to 1, and turn-on curve gets more steeper. In TDR, LVL1 Pt is set to 55-65 GeV, That corresponds to 35-45 GeV 8x8 Calo Cluster Et, giving ~100Hz of LVL1 output rate. Due to yt>25 cut, rates in lower pt region might not be true. (unlikely to have 2KHz by 10 GeV of LVL1 8x8 Calo cluster Et.) Not exactly sure what’s happening. - need more investigation. For this talk, everything is based on Atlfast Pt. TDR 4jets w/o btag

  4. How Much Can We Lower the Pt Threshold at LVL1 ? Assume that a realistic limit of LVL1 output rate for our jet trigger is a few KHz in the default table. (total 40 -> 100 KHz) This limits lowering threshold rather than LVL2 reduction rate with FTK. LVL1 : To give ~1KHz of LVL1 output, Pt threshold for 4jets is ~40 GeV. TDR : Pt>55-65 GeV, ~200Hz. LVL2 : In any case LVL2 output has to be an order of ~10Hz. TDR : Pt>90-110 GeV, ~10-20Hz. So trying to keep 40GeV even @ LVL2 and reduce LVL2 output rate to ~10Hz by only requiring btagging. 1 btag 2 btag 3 btag 4 btag

  5. LVL2 Reduction by btagging Due to contents of b quarks, The reduction rate is not simple linear dependency w.r.t. Ru (light jet rejection factor). - Compare dotted lines with solid lines Why is real reduction rate higher than slope of 1 ? (1) 4jets with |eta| < 3.2 (2) 4jets with |eta| < 2.5 & N-btag So eff. of N(eta<2.5)/N(eta<3.2) is included. Denominator : N(eta<2.5) * Need to check bb production.

  6. Setting up working points for the cases w/ and w/o FTK Conditions to be considered : (1) Pt cut @ LVL1 can not be lowered below 40 GeV (limited by LVL1 output rate) (2) Pt cut @ LVL2 can be changed by requiring btag. But it has to give the same LVL2 rate as Pt>110 GeV w/o btag (TDR) A ~10Hz w/o FTK B C w/ FTK LVL1 limit

  7. Trigger Rate vs Signal Efficiency In each line from right to left, each point comes from 20,30,40, …….. GeV Pt cut. 20 2 btag 1 btag 30 40 50 A(110) A B(40) C(40) Signal acceptance is increased by a factor of 10-20 by btagging, while keeping LVL2 output rate around 10Hz !

  8. Improvement at Trigger Level Btagging efficiency : 50% @ L = 30 fb^-1

  9. Optimization to see (Final) Improvements w/ and w/o FTK Since optimization can be done in offline, (i.e. using offline quality btag), Only difference between w/o and w/ FTK is 4th jet pt threshold (110 and 40 GeV) - Looked at up to (300,200,120,120), 10 GeV step and up to 4 btags. @ L = 30 fb^-1 Optimized by S/sqrt(S+B), not very stable due to low stat and tight cuts.

  10. w/o FTK w/ FTK Very Quick Look *** Note *** This is very preliminary & optimistic, because there is no bb production taken into account. And also signal cross section used is slightly larger than TDR. Need more study to say something conclusive. But relative improvement looks very nice and promising. 700

  11. Summary > By requiring high quality btagging by FTK at LVL2, we can lower the pt threshold to 40 from 110 GeV while keeping ~10Hz of LVL2 output rate and ~1KHz of LVL1 output. > At Trigger level, this gives significance improvement by a factor of 2-10. > After optimization, we still do see good improvement with FTK. Statistical significance gets better by a factor of 2-3 depending on MA. Things to do : > Should look at dijet mass distributions. > Need more careful study on LVL1 parameterization. > Need to look at bb production in Sherpa. > Need Ru vs btag efficiency plot from realistic FTK simulation. > Plan to look at full simulation for signal. > Make conclusions : - How much can tan be improved (lowered) in this channel ? - Can we measure the mass of Higgs by having FTK ? > Documentation.

  12. With Other Final States Obviously 4b channel is not discovery channel But need it for property !

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