Fuks Benjamin CERN - IPHC - U. Strasbourg Monotop phenomenology at the LHC 2 nd Taipei School on FEYNRULES-MADGRAPH for LHC physics National Taiwan Normal University September 04-08, 2013 Benjamin Fuks - 2 nd Taipei School on FR/MG - 08.09.2013 - Monotop phenomenology at the LHC 1
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CERN - IPHC - U. Strasbourg EYNRULES-MADGRAPH · 2nd Taipei School on FEYNRULES-MADGRAPH for LHC physics National Taiwan Normal University September 04-08, 2013 Benjamin Fuks - 2nd
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Fuks Benjamin
CERN - IPHC - U. Strasbourg
Monotop phenomenology at the LHC
2nd Taipei School on FEYNRULES-MADGRAPH for LHC physics
National Taiwan Normal UniversitySeptember 04-08, 2013
Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 -
Monotop phenomenology at the LHC
1
Introduction Monotops Top anomalous couplings Summary
Monotop phenomenology at the LHC Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 - 2
Introduction Monotops Top anomalous couplings Summary
Monotop phenomenology at the LHC Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 - 5
The top-down approach: pros and cons (2)
✤ How to relate observations to a given model?✤ Assuming a model, how to related the observations to a specific benchmark?✤ How to disentangle models and benchmarks?
✤ Are we missing some signatures not predicted by any model?(and not phenomenologically and experimentally investigated)
THE BOTTOM-UP approach: ✤ We start from the signature✤ We construct an appropriate effective theory✤ Prospective studies at colliders
Monotop phenomenology at the LHC Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 -
Introduction Monotops Top anomalous couplings Summary
Outline
6
1. Bottom-up new physics excursions: why and how
2. Monotops
3. A new search for top anomalous couplings
4. Summary
Monotop phenomenology at the LHC Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 -
Introduction Monotops Top anomalous couplings Summary
7
Monotops at hadron colliders: main features
✦ The bottom-up strategy: we start from a final state signature: top + missing energy
✦Key features:✤ Missing energy (dark matter candidate)
★ Bosonic or fermonic state★ One-particle or n-particle state★ Neutral, weakly-interacting, long-lived/stable/invisible
✤ One single top quark✤ Enhanced coupling between the third generation and the others✤ Initial state: two possibilities
★ A down-type (anti)quark pair → baryon-number-violating process★ An up-type quark / gluon associated pair → flavor-changing neutral interactions
✦ Highly-suppressed in the Standard Model✤ Loop-suppression✤ GIM-suppression
The instrumental background is expected to be highly suppressedIt is fair to consider as only source of background: . ➟ Z ! ⌫⌫ + 3 jets
✦ Additional specific monotop search strategy: we have exactly one top✤ Exactly 3 jets, with one b-tag✤ Lepton veto✤ The two light jets are issued from a W-boson (reconstructed invariant mass)✤ The three jets are issued from a top (reconstructed invariant mass)
Monotop phenomenology at the LHC Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 -
Introduction Monotops Top anomalous couplings Summary
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Monotops with 1 fb-1 of 7 TeV LHC data (2)
✦ The key selection: the missing energy✤ Resonant and non-resonant production have different missing energy spectra
Invisible Z background
Flavor-changing modes
Resonant mode, far from threshold
Resonant mode, close to threshold
➟This selection criterion drives the sensitivity to the different modes
Monotop phenomenology at the LHC Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 -
Introduction Monotops Top anomalous couplings Summary
21
Current bounds on top anomalous couplings
✦ Strong anomalous couplings✤ From single top processes at the production level
★ 1 lepton + 1 b jet + missing energy★ Additional kinematics information (small top transverse-momentum, ...)★ Best bounds (in terms of top rare branching ratio):
BR(t → gu) < 5.7 10-5 and BR(t → gc) < 2.7 10-4
✦ Weak anomalous couplings✤ From rare decays in top-antitop events
★ 3 lepton + 2 jets (1 b-tag) + missing energy★ Leptonic top and Z reconstruction★ Best bounds (in terms of top rare branching ratio):
BR(t → Zq) < 7. 10-4
L =X
q=u,c
p2gs
gqt
⇤t�µ⌫Ta(f
Lq PL+fR
q PR)q Gaµ⌫ +
gp2cW
zqt
⇤t�µ⌫(fL
q PL+fRq PR)q Zµ⌫
�+ h.c.
gqt/⇤
[ ATLAS, 7 TeV, 2.05 fb-1 ]
zqt/⇤
[ CMS, 8 TeV, 19.5 fb-1 ]
We will probe both couplings at the same time, as well as .➟ ⇣
Monotop phenomenology at the LHC Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 -
Introduction Monotops Top anomalous couplings Summary
22
✦ Selection strategy: exploiting the final state topology✤ 3 leptons✤ 2 of them compatible with a Z-boson (same flavor, opposite charge, invariant mass)✤ > 30 GeV✤ W-transverse mass larger than 10 GeV✤ At least one jet and exactly one b-tag✤Top reconstruction
Monotop phenomenology at the LHC Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 -
Introduction Monotops Top anomalous couplings Summary
Outline
24
1. Bottom-up new physics excursions: why and how
2. Monotops
3. A new search for top anomalous couplings
4. Summary
Monotop phenomenology at the LHC Benjamin Fuks - 2nd Taipei School on FR/MG - 08.09.2013 -
Introduction Monotops Top anomalous couplings Summary
25
Summary
✦ We exploit the FEYNRULES - MADGRAPH - PYTHIA - DELPHES - MADANALYSIS 5 framework✤ We develop simplified models describing monotop and multitop signatures✤ We investigate their phenomenology at 7 TeV and 8 TeV
✦ Monotops✤ We study the production of a hadronic top quark in associated with missing energy✤ A large part of the parameter space can be probed by the LHC
(including fairly large masses)
✦ Top anomalous couplings✤ We use associated top-Z production to probe top anomalous couplings✤ This is a competitive channel to put extra constraints on BR(t → Zq)