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E6 GUT Model and the Higgs boson search

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E6 GUT model & the
Higgs boson search
Gökhan Ünel / UC Irvine & CERN
Saleh Sultansoy / Ankara
11 October 2006
Flavour at the LHC workshop

Published in: Technology, Education
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E6 GUT Model and the Higgs boson search

  1. 1. E6 GUT model & the Higgs boson search Gökhan Ünel / UC Irvine & CERN Saleh Sultansoy / Ankara 11 October 2006 Flavour at the LHC workshop
  2. 2. Recall the model 2 uL cL tL , uR, dR, DL, DR , cR, sR, SL, SR ,tR, bR, BL, BR dL sL bL D, S, B: New iso-singlet quarks (Q=−⅓) √ 4παemLD = √ uθ γα (1 − γ5 ) d cos φ + uθ γα (1 − γ5 ) D sin φ W α ¯ ¯ (1) 2 2 sin θW √ 4παem sin φ cos φ ¯ − dγα (1 − γ5 ) D Z α 4 sin θW cos θW √ 4παem ¯ ¯ − Dγα 4 sin2 θW − 3 sin2 φ(1 − γ5 ) D + dγα 4 sin2 θW − 3 cos2 φ(1 − γ5 ) d Z α + h.c. 12 cos θW sin θW θ : CKM mixing angle The measured values of CKM elements & unitarity ϕ : d - D mixing angle of the 3x4 CKM rows constrains ϕ : sin ϕ < 0.07 .Assumptions: 1. In-family mixing bigger than between family mixing 2. D quark is the lightest, like SM: most accessible in LHC 3. E6 gauge bosons heavy & don’t interact w/ SM bosons
  3. 3. Higgs Interaction 3• The D-d mixing, before the SSB,will introduce D-h interaction.• A straightforward calculation gives: mD ¯ LM h = sin2 φL DM DM h ν sin φL cos φL ¯ M − D (1 − γ 5 ) mD + (1 + γ 5 ) md dM h 2ν• New width calculation sin φL cos φL ¯M − d (1 + γ 5 ) mD + (1 − γ 5 ) md DM h 2ν isosinglet D quark width md ¯ 10 + cos2 φL dM dM h! (GeV) ν 1 -1 10 Illustrative case: mH=120 GeV, sinϕ=0.045, -2 blue=w/ Higgs IA, 10 black=w/o Higgs IA -3 10 200 400 600 800 1000 1200 1400 1600 MD(GeV)
  4. 4. New cross sections & BRs 4 100 DD pair production at LHC BR 6 10 90! (fb) 5 80 10 Total cross section 70 g-g contribution 10 4 _ q-q contribution 60 3 50 10 40 10 2 30 20 10 10 1 0 200 300 400 500 600 700 800 900 1000 200 300 400 500 600 700 800 MD(GeV) MD(GeV) • if mD ~250 GeV, then pair production σ~105 fb. • D decay BRs for a light Higgs (120..135GeV), depend on mD. For high mD (>700GeV) 50, 25 & 25% for W, Z & h modes.
  5. 5. Impact on Higgs searches 5 PHYSICS PERFORMA Signal significance H !!! "!"! !"! WH, ttH (H !!! "!"!) WH, ttH (H !!! bb) (*) H !!! ZZ !!! 4 l H !!! WW (*) !!! l#l# source: ATLAS TDR 10 2 H !!! ZZ !!! ll## H !!! WW !!! l#jj Total significance• Could we use the D quarks to improve the Higgs search potential of ATLAS? 10• Consider: 5$ • D quark pair production • a light Higgs -1 100 fb (no K-factors) 1 2 3 10 10 mH (GeV) BR(H→γγ )=0.2% at mH=120 GeV, best significance is from H→γγ channel, 8σ at 100fb-1
  6. 6. MC study on h discovery 6 D1 D2 BR #expected Higgs/100fb−1 expected final state D → hj D → hj 0.029 (0.053) 0.58×106 (2.65×104 ) 2j 4jb D → hj D→Zj 0.092 (0.120) 0.92×106 (3.0×104 ) 2j 2jb 2l D → hj D→Wj 0.190 (0.235) 1.9×106 ( 5.88×104 ) 2j 2jb l ET,miss• >3x106 (>1x105) additional Higgs bosons at LHC, if mD=250 (500) GeV ‣enough to motivate a study for 250, 500, 750 & 1000 GeV quarks using the 2j 2jb l ET miss signal • SM background: W jb jb j j events, 80% from t-t background • Signal implemented in CompHEP, bg from MadGraph, simulation in athena 11.0.41 using ATLfast • Final analysis done with physics objects in Root • Generator level cuts are: |ηp | ≤ 3.2 , PT p ≥ 20 GeV , Rp > 0.4
  7. 7. Event Kinematics 7 • Example for mD = 500 GeV t G b-je t igna l B ha rd je spdf pdf pdf 0.1 BG 0.09 0.07 a l sign 0.08 0.06 0.08 0.07 0.05 0.06 0.06 BG jet 0.04 rd 0.05 a n al h Sig 0.04 0.03 0.04 BG 0.03 0.02 0.02 0.02 0.01 0.01 00 50 100 150 200 250 300 350 400 450 500 0 -0.8 -0.6 -0.4 -0.2 0 -1 0.2 0.4 0.6 0.8 1 00 200 400 600 800 1000 1200 1400 PT GeV cos ! jb jb HT GeV PT jet jb HT = ∑ |PT | particles θ jb
  8. 8. D and H Reconstruction 1/2 8 cut value % si % bg • Only e & μ are considered for W decays #lep = 1 82.6 79.1 • Missing ET is assumed to come from ν #jet = 4 #bjet =2 98.7 33.7 99.4 36.2 • Analysis cuts (example at mD = 750 GeV) are : PT lep>20 GeV 96.0 93.5 • only HT & PTjet optimized PT jet>140 GeV cosθjet > -0.8 86.3 97.8 36.2 90.4 Mjet−jet > 90 GeV 99.9 83.1 HT > 1300 GeV 77.0 20.2#events/20GeV/10fb^-1 #events/20GeV/10fb^-1 ∆mD < 100 GeV 55.7 32.9 2500 3500 V 0 Ge GeV combined 9.54 0.48 2000 25 GeV 3000 2 50 GeV = 20 = 20 m =1 D 2500 mD = 1 --- SM background 1500 mH 2000 mH ++ Signal 1000 1500 10fb-1 1000 ✓ With these parameters, 500 using 10fb-1 integrated 500 0 luminosity, both the Higgs 0 100 200 300 400 500 600 700 800 9001000 0 0 50 100 150 200 250 300 350 400 Mbj - bj (GeV) boson and the D quark can be discovered. GeV Reconstructed Reconstructed invariant mass of D invariant mass of h
  9. 9. D and H Reconstruction 2/2 9 Figure 6: The reconstructed masses for the Higgs particles for different D quark mass values of 250 fb−1 integrated luminosities.•For higher D quark masses lets concentrate only on Higgs searches: 8000 #events/16GeV/100fb^-1 #events/16GeV/3000fb^-1 #events/20GeV/30fb^-1 70 mD = 500 GeV 7000 mD = 750 GeV 300 #events/16GeV/300fb^-1 60 #events/20GeV/30fb^-1 180 6000 250 250 160 50 5000 200 140 40 200 4000 120 150 100 3000 30fb-1 30 150 300fb-1 100 80 2000 20 100 60 1000 50 10 40 0 50 0 0 100 200 300 400 500 600 700 800 900 1000 00 50 100 150 200 250 300 350 400 0 20 MD (GeV) Mbj - bj (GeV) 00 50 100 150 200 250 300 350 400 00 50 100 150 200 250 300 350 400 GeV GeV Table III: The expected number of signal (S) and background (B) events for D quark and Higgs • 30fb ∫Luminosity yields: -1 luminosity. The counted events are in a range of ±50 GeV (±20 GeV) from the generator level valu MD (GeV) 250 500 750 1000 S 8802 5303 336 222 27 19 1.9 1.4 B 29379 31717 313 321 32 56 3.1 10.6 √ S/ B + S 45.1 27.6 13.2 9.5 3.5 2.1 0.84 0.42
  10. 10. Higgs and D signal reach 10 L ( fb-1)• 5σ Higgs discovery 10 3 from DD→Whjj 5! H boson discovery 5! D quark discovery 3! H boson signal channel can be made in 3! D quark signal 10 2 one year of running at design luminosity if mD <700 GeV 10• If mD<630 GeV, this channel becomes as 1 efficient as H→γγ . (i.e. 8σ in 100 fb-1) -1 10 300 400 500 600 700 800 900 1000 MD (GeV)
  11. 11. Outlook 11‣ The 3 sigma signal from a light Higgs, can be seen within a year (100 fb-1) via the E6 quarks if mQ< 800 GeV.‣ The outcome should be checked against the full simulation (Geant) results. (working for a CSC note)‣ The impact of the heavy quark(s) to the Higgs production via loop diagrams could be interesting.‣ BG in this analysis is ~20% overestimated: we did σ=2*(W+4j) but σ(W- 4j) = 0.8*σ(W+ 4j)‣ Multi jet background to be checked. (thanks to Juan Antonio for the hint!)

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