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1. chinaXiv:201609.01068 [pdf]

Limits on Excited Quarks from the ATLAS Multi-jet Search

Ning Zhou; Kechen Wang; Kuhan Wang
Subjects: Physics >> Nuclear Physics

We interpret the recent ATLAS multi-jet search results using 20.3 fb-1 data at sqrt(s)=8 TeV in the context of searching for excited quarks. Within the effective field theory framework, using the null results of that search, our analysis shows that the excited quark mass below 5 TeV can be excluded at the 95% confidence level. Our analysis also indicates that when the validation of effective field theory is considered, the limit can be largely compromised.

submitted time 2016-09-20 Hits1934Downloads730 Comment 0

2. chinaXiv:201609.01063 [pdf]

Beyond Higgs Couplings: Probing the Higgs with Angular Observables at Future e$^+$ e$^?$ Colliders

Nathaniel Craig; Jiayin Gu; Zhen Liu; Kechen Wang
Subjects: Physics >> Nuclear Physics

We study angular observables in the?e+e?→ZH→?+??bb??channel at future circular?e+e??colliders such as CEPC and FCC-ee. Taking into account the impact of realistic cut acceptance and detector effects, we forecast the precision of six angular asymmetries at CEPC (FCC-ee) with center-of-mass energy?s√=?240 GeV and 5 (30)?ab?1?integrated luminosity. We then determine the projected sensitivity to a range of operators relevant for the Higgs-strahlung process in the dimension-6 Higgs EFT. Our results show that angular observables provide complementary sensitivity to rate measurements when constraining various tensor structures arising from new physics. We further find that angular asymmetries provide a novel means of both probing BSM corrections to the?HZγ?coupling and constraining the "blind spot" in indirect limits on supersymmetric scalar top partners.

submitted time 2016-09-19 Hits2277Downloads885 Comment 0

3. chinaXiv:201609.00940 [pdf]

Natural Supersymmetry, Muon $g-2$, and the Last Crevices for the Top Squark

B. Paul Padley; Kuver Sinha; Kechen Wang
Subjects: Physics >> Nuclear Physics

We study the interplay of natural supersymmetry and a supersymmetric solution to the discrepancy observed in measurements of the muon magnetic moment. The strongest constraints on the parameter space currently come from chargino searches in the trilepton channel and slepton searches in the dilepton channel at the LHC, and vast regions are currently allowed, especially at large?tanβ. With light top squarks in the spectrum, as required from naturalness arguments, the situation changes dramatically; stop-assisted chargino and neutralino production via?t~→bχ~±1?and?t~→tχ~01?are already probing the entire parameter space compatible with the muon magnetic moment at?tanβ?O(10), while upcoming stop searches will probe most of the parameter space at larger?tanβ?40. Direct Higgsino searches as well as compressed slepton and stop searches are crucial to close out corners of parameter space. We consider one such example: in the presence of light sleptons and charginos as required to obtain appreciable contributions to the muon magnetic moment, compressed stops can dominantly undergo the following decay?t~→b?~ν(ν~?)→b?νχ~01, facilitated by off-shell charginos. We find that the enhanced branching to leptons leads to a?5σ?mass reach (with?3000?fb?1?of data at LHC14) of?mt~?350GeV, with the mass difference between stops and the lightest neutralino being??80?GeV. This will further close out a significant part of the parameter space compatible with naturalness and the muon magnetic moment.

submitted time 2016-09-13 Hits637Downloads373 Comment 0

4. chinaXiv:201609.00050 [pdf]

Distinguishing Dirac/Majorana Sterile Neutrinos at the LHC

Claudio O. Dib; C. S. Kim; Kechen Wang; Jue Zhang?
Subjects: Physics >> Nuclear Physics

We study the purely leptonic decays of W±→e±e±μ?ν and μ±μ±e?ν produced at the LHC, induced by sterile neutrinos with mass mN below MW in the intermediate state. Since the final state neutrino escapes detection, one cannot tell whether this process violates lepton number, what would indicate a Majorana character for the intermediate sterile neutrino. Our study shows that when the sterile neutrino mixings with electrons and muons are different enough, one can still discriminate between the Dirac and Majorana character of this intermediate neutrino by simply counting and comparing the above decay rates. After performing collider simulations and statistical analysis, we find that at the 14 TeV LHC with an integrated luminosity of 3000 fb?1, for two benchmark scenarios mN = 20 GeV and 50 GeV, at least a 3σ level of exclusion on the Dirac case can be achieved for disparities as mild as e.g. |UNe|2<0.7 |UNμ|2 or |UNμ|2<0.7 |UNe|2, provided that |UNe|2, |UNμ|2 are both above ?2×10?6.

submitted time 2016-09-05 Hits1089Downloads570 Comment 0

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