A charged Z to explain the apparent disagreement
- Slides: 23
A charged Z' to explain the apparent disagreement in topantitop asymmetries between Tevatron and LHC 10/7/2020 Estefanía Coluccio Leskow (In collaboration with E. Álvarez) Buenos Aires University (UBA) ICHEP 2012 7/6/12 Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
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. 10/7/2020 4 - Results 5 - Conclusions Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
1 - Introduction Top Quark Asymmetries at Tevatron and LHC Forward-Backward Asymmetry Invariant under boosts 10/7/2020 Charge Asymmetry LHC: LHC symmetric initial state Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
At Tevatron: Tevatron 1 - Introduction (p-value=0. 006) At LHC: 10/7/2020 Is there anything wrong? OR Could both be explained simultaneously!? Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
2 - 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: 10/7/2020 Blue Region: Same sign-tops constraint! Model EXCLUDED (CMS PAS SUS-11 -020) Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
3 - Z' Model The New Phenomenological term of the Lagrangean is given Some remarks: Left handed coupling constrained by b physics Mz' > m t (avoids Flavour Change Top Decay) 10/7/2020 No same sign tops production Atomic parity violation (arxiv: 1203. 1320) no constraint! relaxed because Z'N and Mz' > m t constraints at the LHC relaxed by making larger (DM? , Invisible? ) (arxiv: 1203. 4489, ATLAS-CONF-2011 -100. , ATLAS-CONF-2011 -121, ATLAS-CONF-2011 -142, CMS PAS TOP-11 -005, ) Asymmetry cancellation at LHC not present at Tevatron COULD EXPLAIN RESULTS!! Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
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 10/7/2020 s- channel: Ac < 0 Needs gluons and Phase space so “ switched on “ At LHC! Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
3 - Z' Model How do we search for the cancellation? Using MADGRAPH we simulate: SM + NP We make a 2 test with the last measurements at: Tevatron: LHC: 10/7/2020 Region of parameter space: Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
4 - Results: t – channel contribution Positive Ac Ac (NP) > 0 Ac (NP) < 0 10/7/2020 Numbers: Difference (in measured values. ) to Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
4 - Results s – channel contribution Negative Ac Ac (NP) > 0 Ac (NP) < 0 10/7/2020 Numbers: Difference (in measured values. ) to Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
4 - Results All : Expected Cancellation!! Ac (NP) > 0 Ac (NP) < 0 10/7/2020 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. . . Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
4 - Results ' ' 3* ' Larger allowed regio Only s-channel controlled by the width Tevatron's results are safe! 10/7/2020 But still. . Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
4 - Results ' ' 3* ' ' ' 5* ' ' ' 7* ' Limit by LHC with 0. 7 fb-1 10/7/2020 ---- Expected Limit with 5 fb-1 Reference Point: f. R=0. 7, MZ' =225 Ge. V Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
4 - Results Distinctive features of the Model ZC' Model Low p. T Channel-s OFF 10/7/2020 Channel-t ON AC > 0 High p. T Channel-s ON Channel-t OFF AC Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
4 - Results Other differential observables of the Model ZC' Model 10/7/2020 Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
And what about the AFB at Tevatron ? ZC' Model 10/7/2020 Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
Conclusions Charged FC”N”C Z': All Tevatron All LHC Increase in Z' width: Atomic Parity Violation: 10/7/2020 Prediction: Ac vs. p. T tj resonance search Increase in Z' width see talk by Merlin Davies for Atlas. Increase Single Top Production (~ %20, new search strategy required. . . ) Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
10/7/2020 Thank you! Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
Back - Up Slides 10/7/2020 Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
10/7/2020 Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
10/7/2020 Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
10/7/2020 Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012
10/7/2020 Estefanía Coluccio Leskow - Top Quark Physics - ICHEP 2012