Top Quarks and New Physics

Transcription

1 Top Quarks and New Physics James Wells PASCOS, July 2011 aps.org 1

2 top quark special * Most massive and strongly interachng with EWSB * Flavor physics and other tests not as stringent as lighter flavors opportunihes for discovery * Tevatron "anomaly" with AFB(tops) we will discuss this LHC now over 4x number of tops 2

3 Top Asymmetry at the Tevatron t p θ pbar tbar Assuming CP which implies where 3

4 Standard Model PredicHon Asymmetry arises at α s 3 order. (Close analogy with QED α 3 asymmetry, Berends et al. 1973) Interference of ISR with FSR: Interference of box with tree: A FB (th) = % 4

5 Tevatron Measurement Ref: CDF note 10436,

6 Large BSM contribuhon difficult: Illustrate with Axigluons So- called chiral color theories of various origins. SU(3) L x SU(3) R breaks to SU(3) c Leaving 8 massive axigluons. Coupling is QCD strength but with γ 5 Problem is the asymmetry goes wrong way! A FB = for m A = 1 TeV Limit on pure axigluon from A FB (t) may be stronger than from direct searches. 6

7 Try more general g V - g A couplings x Couplings are with respect to the QCD gauge coupling. This point looks good! x Ferrario, Rodrigo, Pure axigluon coupling (large negahve contribuhon to A FB ) 7

8 Top cross- sechon constraint x Consistency with total rate is ok. Ferrario, Rodrigo,

9 Generic Problem: Difficulty with differenhal cross- sechon Data from CDF, Measurement of the mbar differenhal cross sechon in 2.7 o - 1 of CDF II Data, CDF note 9602 (11 Nov 08). ICHEP 2010 Red line: M X =1.2 TeV g V =1.65 g A =1.55 9

10 s- channel fixes very challenging For s- channel colored and parity- violahng and flavor- diagonal Z /axigluon: Have Z /axigluon couple with to uubar and mbar with opposite sign - > posi%ve asymmetry Have Z /axigluon mass be greater than 1 TeV - > keep direct rate down Have Z /axigluon couple with less magnitude to uubar than mbar - > keep direct qqbar dijet rate much lower than 9bar rate Hard to make it all fit together with A FB >10% and evade Tevatron & LHC bounds. LHC would find it already/soon. See Y. Bai et al

11 A FB from t- channel physics Jung, Murayama, Pierce, JW [ ] 11

12 V contribuhons to Wjj CDF: events in ~ 150 GeV jj mass peak in 4.3 o - 1 D0 not seeing it resoluhon in the works 12

13 A FB and inclusive mbar at the LHC Jung, Pierce, Murayama, JW, 09 * * * is a choice of M Z mass and α X compahble with A FB and σ(mbar) 13

14 Like- sign top quarks In most basic V - u- t or V - d- t models, there is nothing to prevent the produchon of like- sign top quarks. These two applicable if M Z' > M t CMS [ ] 14

15 Like- sign top quarks (cont.) σ(pp- >m(j)) < 17 pb at 95% CL CMS [ ] EssenHally all simple t- channel A FB ideas are ruled out. 15

16 More complicated t- channel physics Basic s- channel and basic t- channel explanahons of AFB are not working, for different reasons. s- channel looks more problemahc to salvage than t- channel ideas. Two t- channel ideas: Non- abelian horizontal symmetry: Jung, Pierce, JW, 11 Top quark condensate theories: Cui, Han, Schwartz, 11 16

17 Non- abelian Extension Put (t b) R together in an SU(2) doublet. W + and W - raises and lowers top number Z does not change top number Thus, it is the W bosons that are exchanged in t- channel to produce the large asymmetry Difference of W and Z masses allows mismatch between couplings to quark gauge and mass eigenstates: c=cos(θ) 17

18 Like- sign top signal is safe for now The conservahon of top number forbids like- sign top quark produchon However, violahons of top number come from the small mismatch angle θ between gauge and mass eigenstate quark interachons with the SU(2) bosons. Processes such as uu - > m are forbidden to order sin 2 θ Example benchmark points * Small θ angle allows W' to decay to uubar over tubar 18

19 Constraints on model A FB =15% for A,B,C LHC 7 TeV predichon: Jung, Pierce, JW,

20 Single Top ProducHon u g t V' t j j b e,µ ν Jung, Pierce, JW, in preparahon 20

21 Top Condensate Theories 21

22 Top condensate parameter space compahbility Cui, Han, Schwartz, 11 22

23 Conclusions A FB (tops) currently shows tension with the SM CompaHbility with other top quark observables (like- sign tops, invariant mass distribuhon, total rate, single top, etc.) is challenging. ResulHng theories are ones that would have never been considered otherwise. A FB (tops) may be correlated with Wjj excess seen at Tevatron, although not necessary and D0 does not see this excess. CriHcal updates of Tevatron analyses: A FB (tops), Wjj and single top especially. LHC analyses to look for: dσ/dm mbar and single top especially. A FB (tops) less likely to show deviahons at this early stage. Careful: some analyses will not collect new physics contribuhons. See next slide 23

24 Standard Model q g b W b so t q' b ν e,µ This is targeted, largest contribuhon to single top in SM CMS analysis: blj + MET for SM signature ("2D analysis") and maybe one extra b ("BDT") New Physics u g t V' t j j b e,µ New Physics: same signature except one extra non- b jet. ν 24