Pair production of heavy Q = 2/3 singlets at LHC

Transcription

1 Pair production of heavy Q = 2/3 singlets at LHC J. A. Aguilar-Saavedra Univ. Granada & CFTP, IST Lisbon TOP 2006, Coimbra, January 12 th 2006

2 Summary Overview of the model 1 Overview of the model 2 3

3 Overview of the model Addition of one SU(2) L singlet T with charge Q = 2/3 extra dimensions, little Higgs models, GUTs Anomalies Mass matrix of Q = 2/3 quarks with seesaw structure M u = v 2 Y u, B u bare mass term or from Higgs singlet ( ) M u M u = = B u m 11 m 12 m 13 m 14 m 21 m 22 m 23 m 24 m 31 m 32 m 33 m 34 B 1 B 2 B 3 B 4

4 Mixing with singlet [ modifies interactions with W, Z and H does not affect interactions with γ, g L W = g ] [ūγ µ V P L d W µ + + dγ µ V 3 P L u Wµ 2 L Z = g [ ūγ µ P L 4 ] 2c W 3 s2 W u Z µ g L H = ū [ M u P L + M u ] P R u H 2M W

5 Mixing with singlet [ modifies interactions with W, Z and H does not affect interactions with γ, g L W = g ] [ūγ µ V 4 3 P L d W µ + + dγ µ V 4 3 P Lu Wµ 2 L Z = g [ ūγ µ X P L 4 ] 2c W 3 s2 W u Z µ g L H = ū [ M u XP L + X M u ] P R u H 2M W X = VV

6 In particular: New quark T has a CC coupling V Tb to the b quark (V Td, V Ts much smaller) See more T has a FCN coupling to the top and Z boson X tt 2 V Tb 2 (1 V Tb 2 ) V tb smaller than unity: V tb 2 = 1 V ub 2 V cb 2 V Tb 2 1 V Tb 2 Z t L t L coupling also smaller: c L = s2 W c L = X tt 4 3 s2 W, with X tt V tb 2

7 Signals at LHC Overview of the model Production of the new quark T QCD pair production pp TT [Aguila et al., NPB 90] EW single production pp Tj [Han et al., PRD 03] FCN processes involving the top quark [JAAS, APPB 04] Rare top decays t Zq, t Hq (q = u, c) Single top production gq Zt, gq Ht

8 Signals at LHC Overview of the model Production of the new quark T QCD pair production pp TT [ larger σ for moderate mt σ independent of V Tb EW single production pp Tj [Han et al., PRD 03] FCN processes involving the top quark [JAAS, APPB 04] Rare top decays t Zq, t Hq (q = u, c) Single top production gq Zt, gq Ht

9 Signals at LHC Overview of the model Production of the new quark T QCD pair production pp TT [Aguila et al., NPB 90] [ σ VTb 2 EW single production pp Tj larger σ for 1 TeV FCN processes involving the top quark [JAAS, APPB 04] Rare top decays t Zq, t Hq (q = u, c) Single top production gq Zt, gq Ht

10 Decays of T (M H = 115 GeV) 500 GeV 1 TeV Br(T W + b) Br(T Zt) Br(T Ht) Decay T W + b: the same final states as for a top quark (4 th generation T may have decays T W + B with B W t) Additional decays T Zt, T Ht establish that T is a singlet T Ht discovery channel for a light Higgs boson

11 We study TT production in the channel TT W + bw b with one W decaying leptonically and the other one hadronically We consider = 500 GeV, = 1 TeV [JAAS, PLB 05] Event generation done with our own MC generators (TT, t t, t bj) and ALPGEN (Wb bjj, Zb bjj) Analysis done with PYTHIA + ATLFAST b tagging efficiency of 60% (50%) for low (high) luminosity phase

12 We require a final state with: one isolated charged lepton two b-tagged jets at least two additional jets with η 2.5, p t 20 GeV Additional signal contributions fro Zt, T Ht decays: TT W + b H t, Ht W b W + b W b H TT W + b Z t, Zt W b W + b W b Z (H b b, c c) (Z jj, b b, ν ν)

13 We require a final state with: one isolated charged lepton two b-tagged jets at least two additional jets with η 2.5, p t 20 GeV Additional signal contributions fro Zt, T Ht decays: TT W + b H t, Ht W b W + b W b H TT W + b Z t, Zt W b W + b W b Z (H b b, c c) (Z jj, b b, ν ν)

14 We require a final state with: one isolated charged lepton two b-tagged jets at least two additional jets with η 2.5, p t 20 GeV Additional signal contributions fro Zt, T Ht decays: TT W + b H t, Ht W b W + b W b H TT W + b Z t, Zt W b W + b W b Z (H b b, c c) (Z jj, b b, ν ν)

15 Signal and background cross sections Process σ eff Process σ eff T T (500) 37.3 fb t t 18.8 pb fb (H) Wb bjj 1.23 pb fb (Z) Zb bjj 246 fb T T (1000) fb t bj 710 fb fb (H) fb (Z)

16 We require high transverse momentum for the charged lepton and jets = 500 GeV p lep t p j,max t pt b,max 50 GeV 250 GeV 150 GeV H T 1000 GeV 50 GeV p t 600 GeV = 1 TeV p lep t p j,max t p b,max t 200 GeV 400 GeV 300 GeV H T 1800 GeV 50 GeV p t 400 GeV Reconstruction done looking for two particles of equal mass m(l ν b 1 ) = m( j 1 j 2 b 2 )

17 Signals and backgrounds after cuts ( = 500 GeV) Process N cut N peak T T (H) (Z) t t Wb bjj Zb bjj t bj 70 11

18 = 500 GeV, 10 fb σ evidence ( GeV) SM SM + T (500) 150 SM SM + T (500) Events / 20 GeV 100 Events / 20 GeV lep had SM = t t, Wb bjj, Zb bjj, t bj T = TT W + b W b l ± νb bjj + H, Z contributions

19 Signals and backgrounds after cuts ( = 1 TeV) Process N cut N peak T T (H) (Z) t t Wb bjj Zb bjj 19 1 t bj 3 0

20 = 1 TeV, 300 fb σ evidence ( GeV) SM SM + T (1000) 50 SM SM + T (1000) Events / 100 GeV Events / 100 GeV lep had SM = t t, Wb bjj, Zb bjj, t bj T = TT W + b W b l ± νb bjj + H, Z contributions

21 More details... Overview of the model p lep t cut substantially reduces the T T (H) and T T (Z) signals (Cut required to reduce backgrounds) Events / 20 GeV TT TT (H) TT (Z) tt Events / 20 GeV TT TT (H) TT (Z) tt lep p t Distributions for 2000 events, without cuts lep p t

22 More details... Overview of the model For = 500 GeV, T T (H) and T T (Z) signals have a sizeable contribution around the peak Events / 20 GeV TT TT (H) TT (Z) tt Events / 20 GeV TT TT (H) TT (Z) tt lep Distributions for 2000 events, without cuts had

23 More details... Overview of the model For = 1 TeV, T T (H) and T T (Z) signals are widely distributed across the m lep T and mhad T range Events / 20 GeV TT TT (H) TT (Z) tt Events / 20 GeV TT TT (H) TT (Z) tt lep Distributions for 2000 events, without cuts had

24 LHC reach for Q = 2/3 singlets For = 500 GeV, 5 σ evidence achieved with 2.1 fb 1 Eventually, 1.1 TeV can be reached with 300 fb T = T = σ discovery (TT) 5σ discovery (Tj) 95% bound (T / U=0) 95% bound (T) Tj scaled V Tb 0.1 from ATLAS result [Azuelos et al., EPJC 05] More details

25 LHC reach for Q = 2/3 singlets If Q = 2/3 singlets not observed at LHC limits on, V Tb T = T = % bound (TT) 95% bound (Tj) 95% bound (T / U = 0) 95% bound (T) V Tb

26 Conclusions Overview of the model New T singlets with a mass up to 1 TeV can be observed at LHC (with a mass around 500 GeV they will be quickly discovered) In addition to direct observation, Q = 2/3 singlets may give indirect effects in low energy physics: CP asymmetries in B decays δm Bs, δm D Rare kaon decays as well as in top physics: top FCN decays t qz e + e t t (ILC)

27 Additional slides and V Tb dependence of TT, Tj production Allowed range for CKM elements Anomaly cancellation tr[t a t b Y] = 1 2 δab q Y q = ( 2 ) = 0 tr[τ a τ b Y] = 1 2 δab f,d Y f = 0 tr[y 3 ] = f tr[y] = f Y 3 f = Y f = ( 2 3) 3 + ( ) 2 3 = 0 3 ( 2 ) = 0 Back

28 Additional slides and V Tb dependence of TT, Tj production Allowed range for CKM elements Indirect constraints on V Tb V Tb constrained by the T parameter T = N c 16πs 2 W c2 W { VTb 2 [θ + (y T, y b ) θ + (y t, y b )] X tt 2 θ + (y T, y t ) } [Lavoura, Silva, PRD 93] [JAAS, PRD 03] plus other model-dependent new physics contributions (ignored) Experimentally T = 0.17 ± 0.12 (U arbitrary) T = 0.12 ± 0.10 (U = 0) 95% bounds on V Tb Back More

29 Additional slides and V Tb dependence of TT, Tj production Allowed range for CKM elements Indirect constraints on V Tb Allowed range for V Tb, V tb V Tb V tb Stronger constraints for larger Back More

30 Additional slides and V Tb dependence of TT, Tj production Allowed range for CKM elements dependence of TT, Tj production V Tb m t / expected from mass matrix diagonalisation... but V Tb = m t / too large for 900 GeV TT Tj (V Tb = 0.1) Tj (T = 0.12) 0.2 V Tb (T = 0.12) V Tb = m t / 95% bound (T / U = 0) 95% bound (T) σ (fb) 10 2 V Tb T = T = Back

31 Additional slides and V Tb dependence of TT, Tj production Allowed range for CKM elements Allowed range for V td, V ts Experimental data from K, B physics constraints on V td, V ts V td V ts Stronger constraints for larger Back

32 Additional slides and V Tb dependence of TT, Tj production Allowed range for CKM elements Allowed range for X tt X tt