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Physics results at D Ø

Physics results at D Ø. The Tevatron and D Ø are mature, and are operating stably. We expect no further upgrades to the Collider or detector. Stony Brook has contributed substantially to all phases of the DØ physics program.

larissa-mcintosh
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Physics results at D Ø

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  1. Physics results at DØ The Tevatron and DØ are mature, and are operating stably. We expect no further upgrades to the Collider or detector. Stony Brook has contributed substantially to all phases of the DØ physics program. Our emphasis in the remaining two years of the run will be on high priority legacy measurements. You have heard about the W mass and Higgs search analyses that will form the basis of our future program. In this talk, I discuss some of our other recent physics activities. D0 research - Grannis

  2. 3rd Generation Leptoquarks Y. Hu, P. Grannis PRL 101, 241802 (2008) Leptoquarks with both color and lepton quantum numbers arise in many models for new physics. LQs should couple to fermions within a single generation to avoid FCNCs. New physics is often coupled to the third generation, thus seek pair produced LQ3 by QCD, with decays LQ3tbleading to a final statet+t- bb. Select tau pairs with t1mnnandt2hadrons and require 2 jets, with at least one tagged as b. Final selection requires transverse mass (m MET) <60 GeV to reject top and W+jet background. The distribution in ST (S|pT| for m, th, jets, MET) distinguishes signal and background and allows setting limit on possible LQ3 signal. LQ3 mass limit for coupling b(LQ3,t,b)=1 is 210 GeV. With b=1/2 (50% nt), mass limit is 207 GeV (LQ3nt is phase space suppressed), D0 research - Grannis

  3. Variance matrix Mij = (1/K)Sk (xik-<xi>)(xjk-<xj>); H  M-1 Then can predict the best value for the Nth unknown variable (here jet energy) from xN = <xN>- Sj=1 HjN(xj-<xj> /HNN N-1 Jet energy resolution improvement E. Strauss, P. Grannis, J. Hobbs Improved jet energy resolution is key for improving searches for dijet mass bumps (e.g. Higgs). We implemented a “H matrix” algorithm [R. Engelmann et al, NIM 216, 45 (1983)] for predicting the Nth variable (here jet energy) based on a set of N-1 measured kinematic variables {xi}. Optimize the set of variables (raw jet Ej & transverse width, preshower deposit, annular cone energy, track pT near cluster, etc) and compute H in MC events; use to predict corrected jet energy in data and MC. Achieve 10-15% improvement in s/E. Improvement is insensitive to choice of training sample. (E/Etruth)for Zqq MC for raw E (black), corrected with g+jet MC(red) and Zqq MC (green) (E/Etruth)for data dijets from W in ttbar events for raw E (black) and corrected Zqq MC (red) D0 research - Grannis

  4. Higgs searches with taus K. Tschann-Grimm, S. Chakrabarti, P. Grannis • The search for Higgs in ttjj final states grew out of the LQ3 search with Y. Hu and resulted in the first paper using this channel with 1 fb-1 of data [PRL 102, 251801 (2009)]. • Chakrabarti and Tschann-Grimm have described the ongoing analyses with t(m )t(hadron)+2jets and t(e) t(hadron)+2jets. We are aiming for publication of these using about 6 fb-1 in early 2010. • The current analyses seek the signals W/Z(qq’) H(tt), Z(tt)H(bb), vector boson fusion and gluon gluon fusion with H(tt). • Improvements, aside from addition of more data: • Inclusion of signals feeding the same ttjj final state as above processes from HWW* (~x3 improvement in signal yield at MH=140 GeV) • Use of the improved jet energy resolution discussed above • Adding t(m) t(e)+2jets • Improved methods for combination of multivariate classifiers for different signal processes. D0 research - Grannis

  5. Stony Brook Editorial Boards DØ is now producing ~50 papers per year and ~100 preliminary results for conferences. As much as we would wish that most of the collaboration would read and comment on these results, it is not feasible since the analyses have become very detailed with long and complex analysis notes. Thus the collaboration operates with ~30 Editorial Boards (EBs) that are charged with proactive interaction and review of analyses. All aspects of the analysis are scrutinized – trigger/data sample selection, MC samples, theory cross section uncertainties, object ID, MC reweightings, multivariate analyses, systematic uncertainty assessments, limit setting. [a current Hvvbb analysis note runs to 250 pages with 230 Figures.] Draft papers are examined for clarity and completeness. All this takes considerable effort! Each EB has a chair and typically 4 members. Members of our group have played substantial roles in several EBs. D0 research - Grannis

  6. Stony Brook Editorial Boards • Some recent EB responsibilities: • Single top quarks: first evidence, anomalous top couplings, W’ (McCarthy) • Searches in final states with photons: fermiophobic Higgs, hidden valley dark photons, GMSB, gg anomalies in extra dimensions; long-lived particles in ZZ (Schamberger) • BS properties: BS lifetime, CP violations, BSDS*DS* (Tsybychev) • top quark properties: W helicity, ttbar resonances, top spin correlations, anomalous top couplings (Grannis chair until 10/2009) • Higgs searches jets+MET: Z(nn)H(bb), H(W(ln)W(qq’)), LQ3(nb)LQ3(nb) (Grannis, chair since 9/2009) • W boson properties: W mass, W width, new recoil system modeling method using data (Schamberger, Grannis chair) D0 research - Grannis

  7. Stony Brook DØ In all, Stony Brook physicists from this grant have contributed as primary authors, EB members or Physics Group convener to 42 of the 141 publications in the list (in our proposal) of published or submitted in the past three years. We carry major responsibilities for operation of the liquid argon calorimeters. Our DOE colleagues are responsible for the silicon track trigger. We have had major leadership roles in the experiment. DOE now says publically that they expect to support running the Tevatron through FY11. We can see potential reasons that extending beyond that could even make sense. Our group expects to remain engaged in DØ through its completion, while opening new vistas with ATLAS. Our DØ activities form a strong basis for leadership in ATLAS. D0 research - Grannis

  8. D0 research - Grannis

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