1 / 23

Estefanía Coluccio Leskow (In collaboration with E. Álvarez) Buenos Aires University (UBA)

A charged Z' to explain the apparent disagreement in top-antitop asymmetries between Tevatron and LHC. Estefanía Coluccio Leskow (In collaboration with E. Álvarez) Buenos Aires University (UBA) ICHEP 2012 7/6/12. Outline. 1- Brief Introduction : Top quark asymmetries at LHC and Tevatron.

guy
Télécharger la présentation

Estefanía Coluccio Leskow (In collaboration with E. Álvarez) Buenos Aires University (UBA)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A charged Z' to explain the apparent disagreement in top-antitop asymmetries between Tevatron and LHC Estefanía Coluccio Leskow (In collaboration with E. Álvarez) Buenos Aires University (UBA) ICHEP 2012 7/6/12

  2. Outline 1- Brief Introduction: Top quark asymmetries at LHC and Tevatron. 2- New Physics: New Models try to explain the discrepancies. 3- Z' Model: Model studied to explain the apparent disagreement between the asymmetries. 4- Results 5- Conclusions

  3. 1- Introduction Top Quark Asymmetries at Tevatron and LHC Forward-Backward Asymmetry Invariant under boosts Charge Asymmetry LHC: symmetric initial state

  4. At Tevatron: 1- Introduction (p-value=0.006) At LHC: Is there anything wrong? OR Could both be explained simultaneously!?

  5. 2- New Physics New Physics Models arise to explain the discrepancies. • Extra light gluon G ' with a broad width • Extra Scalars • Extra W ' with d-t-W ' interaction • Extra Z' boson with flavor - conserving interaction • Extra Z' Neutral boson with flavor - violating interaction • …. etc Excluded by LHC Not Excluded by LHC • Extra Z' charged (not electrically) boson with flavour- violating u-t-Z ' interaction given by: Blue Region: Same sign-tops constraint! Model EXCLUDED (CMS PAS SUS-11-020)

  6. 3- Z' Model The New Phenomenological term of the Lagrangean is given by: Some remarks: • Left handed coupling constrained by b physics • Mz' > m t(avoids Flavour Change Top Decay) • No same sign tops production no constraint! • Atomic parity violation relaxed because Z'Nand Mz' > m t • constraints at the LHC relaxed by making larger • Asymmetry cancellation at LHC COULD EXPLAIN not present at TevatronRESULTS!! (arxiv: 1203.1320) (DM?, Invisible?) (arxiv: 1203.4489, ATLAS-CONF-2011-100., ATLAS-CONF-2011-121, ATLAS-CONF-2011-142, CMS PAS TOP-11-005, )

  7. 3- Z' Model Feynmann 's Diagrams involving a Z'C boson So.... there is a cancellation at LHC! t- channel: Ac > 0 Needs antiquarks! So Dominates At Tevatron Needs gluons and Phase space so “ switched on “ At LHC! s- channel: Ac < 0

  8. 3- Z' Model How do we search for the cancellation? • Using MADGRAPH we simulate: Tevatron: LHC: SM + NP • We make a 2 test with the last measurements at: Region of parameter space:

  9. 4- Results Results: t – channel contribution Positive Ac • Ac (NP) > 0 • Ac (NP) < 0 • Numbers: Difference (in ) to measured values.

  10. 4- Results s – channel contribution Negative Ac • Ac (NP) > 0 • Ac (NP) < 0 • Numbers: Difference (in ) to measured values.

  11. 4- Results All : Expected Cancellation!! • Ac (NP) > 0 • Ac (NP) < 0 • Upper Number: Difference (in ) to measured values of Ac. • Lower Number: Difference (in ) to measured values of (1 = %13) . Remember? constraints at the LHC can be relaxed by making larger...

  12. 4- Results '' 3*' '' 3*' Larger allowed region! Only s-channel controlled by the width Tevatron's results are safe! But still....

  13. 4- Results '' 3*' '' 5*' '' 7*' Limit by LHC with 0.7 fb-1 - - - - Expected Limit with 5 fb-1 Reference Point: fR=0.7, MZ' =225 GeV

  14. 4- Results Distinctive features of the Model ZC' Model Low pT Channel-s OFF Channel-t ON AC > 0 High pT Channel-sON Channel-t OFF AC

  15. 4- Results Other differential observables of the Model ZC' Model Z' Model ZC' Model

  16. And what about the AFB at Tevatron ? ZC' Model

  17. Conclusions • Charged FC”N”C Z': All Tevatron All LHC • Increase in Z' width: • Atomic Parity Violation: • Prediction: Ac vs. pT • tj resonance search see talk by Merlin Davies for Atlas. • Increase in Z' width Increase Single Top Production (~ %20, new search strategy required...)

  18. Thank you!

  19. Back - Up Slides

More Related