Introduction Outline LHCATLAS Higgs production and decay VBF

• Introduction Outline – LHC・ATLAS – Higgs production and decay: VBF H->WW->lvjj • • • CP properties of Higgs couplings MC Samples Determination of Higgs property Parameters Sensitive to the Higgs Property Event Selection Significance Correction functions Result Summary 28 -Mar-06 M Kaneda 2

CP properties of Higgs couplings • Higgs 粒子発見後はその様々な性質の測定が次なる課題である。 • HVV coupling: Spin 0のHiggs場と二つのVector Bosonsのcouplingを考 える Ø SM at tree level (CP Even): Ø gauge invariantなanomalous coupling: CP Even: CP Odd: Ref. : : T. Plehn, D. Rainwater, and D. Zeppenfeld Phys. Rev. Let. 88 051801(2002) 28 -Mar-06 M Kaneda 5

MC Samples • Signal: VBF H -> WW -> lvjj( l = e, m) (MH =110 Ge. V-500 Ge. V) – – – SM(Pythia) CP Even(Mad. Graph) CP Odd(Mad. Graph) (これら、anomalous couplingsのsignalの total cross sectionsはSMのものと同じに なる様に補正した) q(forward jet) q e, m W/Z • Background: – W+4 jets(Alpgen + Pythia) – ttbar (Pythia). 28 -Mar-06 M Kaneda q H W W n q(central jet) change these couplings q(forward jet) 6

Parameters Sensitive to the Higgs property Direction of motion of the child in the V rest frame f q 1 f V(W) q 2 f f The Higgs decay point The Higgs rest frame f: : Higgs粒子の静止系において、二つのW粒子から崩壊した それぞれ2つのfermionが作る平面の間の角度。 q: : W粒子の静止系における fermion の運動量の方向と、 Higgs粒子の静止系におけるW粒子の運動量の方向間の角度。 F (f) = C(1 + bcos 2 f) (0<f<p) b G(q) = T. (1 + cos 2(q)) + L. sin 2(q) (0<cosq<1) R : = (L – T ) / (L + T) R Even SM SM Odd Even Odd MH(Ge. V) R, bの理論値 28 -Mar-06 M Kaneda 7

Determination of Higgs property • これらのRとbを用いてCP Even, CP Oddのcouplingが dominantである可能性をexcludeできるかどうかを調べる。 • Correction function – SMのsignalの半分を用い、R, bの分布に対するacceptanceと selectionの効果を補正するcorrection functionを作る。 • Predicted value with correction – このSMのcorrection functionを用いて補正したCP Even, CP OddのR, bの値を求めてSMの場合と比較する。 28 -Mar-06 M Kaneda 8

Event Selection (Trigger Cut) • Only one lepton is required – lepton’s efficiency: 90% – electron: PT > 25 Ge. V, , |h|<2. 5, muon: PT> 20 Ge. V, |h|<2. 5 – Number of leptons = 1 • Forward jets and Central jets – PT >20 Ge. V, |h|<5. 0 – Number of b-jets = 0 – Choose four highest PT jets – Forward jets q(forward jet) e, m q W/Z q • Two outer jets in pseudo rapidity. • Pt > 40 Ge. V • Mj 1 j 2 > 1200 Ge. V, | h 1 - h 2 | >5 – Central jets H W W n q(central jet) q(forward jet) • Two remaining jets • Central Jet Veto : PT > 20 Ge. V, hfj 1 < hfj 2 28 -Mar-06 M Kaneda 9

Event Selection: decay products PT Cut of Lepton, Neutrino and Central jets Decay Particles from W(->lv) m. H <160 Ge. V 160<m. H <200 Ge. V m. H >200 Ge. V PT (PTl and ETmiss) > m. H/8 + 5 Ge. V > m. H/40 + 25 Ge. V Higher PT Cut > m. H/4 + 10 Ge. V > m. H/20 + 50 Ge. V Decay Particles from W(->jj) PT(cj 1, cj 2) Higher PT Cut > 20 Ge. V >m. H/16 + 10 Ge. V > m. H/4 + 10 Ge. V > m. H/20 + 50 Ge. V Isolation of Lepton and Central jets from Forward jets Lepton • hfj 1 < hlepton < hfj 2 • DR (lepton – fj 1, fj 2) > 2 28 -Mar-06 Central Jet • DR (cj 1, cj 2 - fj 1, fj 2) > 1. 5 M Kaneda 10

Event Selection: Mjj (Mass of W->jj) Cut m. H <160 Ge. V m. H >160 Ge. V 60 – (160 - m. H)Ge. V < Mjj < 90 Ge. V 60 Ge. V < Mjj < 90 Ge. V MH=170 Ge. V MH=140 Ge. V Mjj(Ge. V) 28 -Mar-06 M Kaneda Mjj(Ge. V) 11

Event Selection Higgs Mass Constraint • 全体の系 の質量にあるHiggs粒子の質量 q(central jet) Missing ET n を仮定することによって、観測出来ないnの 運動量のビーム軸方向の成分(Evz)を決め Unknown Evz q(central jet) る。 • もし、解けない場合、そのeventは落とす。 W(jj) W(ln) H e, m Higgs Mass (m. H) Constraint Mlv (Mass of W->lv) Cut M(W->lv) < 110 Ge. V 28 -Mar-06 M Kaneda 12

Expected cross sections after selections and Discovery Significance Signal(fb) W+4 jets(fb) ttbar(fb) significance with 10(30)fb-1 140 0. 86 0. 35 0. 04 3. 1(5. 8) 170 1. 95 0. 35 0. 03 6. 7(11. 7) 250 0. 88 0. 29 0. 04 3. 5(6. 5) 400 1. 11 0. 12 0. 04 5. 3(9. 8) Max Significance (Poisson ) MH(Ge. V) 28 -Mar-06 30 fb-1 10 fb-1 M Kaneda MH(Ge. V) 13

Correction functions for MH=170 Ge. V f f No cut and no smearing After smearing and all selections f Correction function for f f cosq 28 -Mar-06 M Kaneda cosq Correction function for cosq 14

Applying correction function (MH=170 Ge. V, 30 fb-1) SM SM CP Even f CP Odd cosq CP Odd f 28 -Mar-06 M Kaneda cosq 15

Result of R and b with 30 fb-1 R R Rの値から、200 Ge. V以上では SMのcouplingとanomalousな couplingを区別することが出来る b 28 -Mar-06 M Kaneda 16

Back Up 28 -Mar-06 M Kaneda 18

Cut values (Ge. V) Cut values of PT of decay particles m. H (Ge. V) 28 -Mar-06 M Kaneda 19

VBF: H->WW->lvjj WW MH(Ge. V) ヒッグスの崩壊率 Signal significance 28 -Mar-06 M Kaneda 20

Discovery potential • We analyzed the data by sliding Higgs mass parameters (m. H) in the selection criteria. From these results, we can estimate true Higgs Mass (MH) and obtain signal significance. 28 -Mar-06 M Kaneda 21

m. H dependence of number of remaining events 10 fb-1 m. H (Ge. V) Background 28 -Mar-06 M Kaneda 22

m. H(Peak) (Ge. V) m. H(Peak) VS true MH m. H(peak) = 1. 07 MH – 4. 39 m. H (Peak): : peak position of the number of remaining events in the previous page, including backgrounds. 28 -Mar-06 M Kaneda 23