DØ Run II single top search

Search for single top quark production at DØ in RunII

M. Agelou, B. Andrieu, P. Baringer, A. Bean, D. Bloch, E.E. Boos, V. Bunichev, E. Busato, L. Christofek, B. Clement, L.V. Dudko, T. Gadfort, A. Garcia-Bellido, G. Gaudio, D. Gele, P. Gutierrez, A.P. Heinson, S. Jabeen, S. Jain, A. Juste, D. Kau, M. Kopal, J. Mitrevski, J. Parsons, P.M. Perea, E. Perez, H.B. Prosper, A. Quadt, V.I. Rud, R. Schwienhorst, M. Strauss, B. Vachon, M. Warsinsky, G. Watts

E-mail conveners: Ann Heinson and Reinhard Schwienhorst

Abstract

We perform a search for single top quarks in two production modes, s-channel (tb) and t-channel (tqb), separately and combined. The search is performed in the electron+jets and muon+jets decay channels, with either a soft-muon tagged jet, a secondary-vertex tagged jet, or a jet-lifetime-probability tagged jet to indicate the presence of a b-jet and thus improve the signal-to-background ratio. We use between 156 and 169 pb^-1 of Run II data, depending on the analysis channel, collected between August 2002 and September 2003. We do not find a statistically significant evidence for a single top signal and therefore set 95% confidence level upper limits on the single top production cross section. The resulting 95% confidence level upper limits on the production cross sections are 19 pb (s-channel), 25 pb (t-channel), and 23 pb (s+t channels).

Description of the analysis

Read the conference note for Summer 2004.

Analysis flow

Plots

Distributions of the number of good jets, the transverse mass of the W boson, and the scalar sum of the transverse energy of the electron, neutrino, and two highest-ET jets, for the electron and muon channel combined for the different background sources. The upper row shows the plots for the combination of JLIP and SLT, the lower row for the combination of SVT and SLT.

Distributions of the number of good jets, the transverse mass of the W boson, and the scalar sum of the transverse energy of the electron, neutrino, and two highest-ET jets, for the electron and muon channel combined. The upper row shows the plots for the combination of JLIP and SLT, the lower row for the combination of SVT and SLT. The sum of the ttbar, W+jets, and fake-lepton background contributions is shown as the gray line with shaded error band. The two signal contributions tb and tqb are multiplied by 10 in the plot.

Tables:

Muon Yields (gif) (eps)
Electron Yields (gif) (eps)
Electron + Muon Yields (gif) (eps)
MC Systematics (gif) (eps)
Data Based Backgrounds Systematics (gif) (eps)

Distributions of the Bayesian posterior probability density for the combination of electron and muon channels for the three different signal channels: s-channel (tb, left), t-channel (tqb, middle), and the combination of s- and t-channels (right).

More plots:

95% C.L. Expected / Measured Upper Limits (after final selections, with systematics) using Bayesian statistics:

Channel	Electron	Muon	e+µ	e+µ (with SLT)
s-channel
SLT	26 / 53	33 / 35	22 / 40
SVT	18 / 14	24 / 27	17 / 14	16 / 19
JLIP	20 / 16	26 / 21	20 / 15	17 / 22
t-channel
SLT	42 / 81	56 / 59	37 / 67
SVT	24 / 20	35 / 41	24 / 20	23 / 25
JLIP	27 / 22	37 / 29	27 / 21	25 / 30
s- and t-channel
SLT	35 / 72	45 /49	30 / 57
SVT	21 / 18	29 / 36	20 / 18	20 / 23
JLIP	24 / 20	32 / 26	23 / 19	22 / 30

Talks:

Pheno 2004 (April); Aran Garcia-Bellido: mu+jets channel
Pheno 2004 (April); Reinhard Schwienhorst: e+jets channel
DPF 2004 (August); Len Christofek: mu+jets channel
DPF 2004 (August); Supriya Jain: e+jets channel

Last modified: Tue Nov 9 12:58:03 CST 2004
by S. Jain and A. Garcia-Bellido

Search for single top quark production at DØ in RunII

M. Agelou, B. Andrieu, P. Baringer, A. Bean, D. Bloch, E.E. Boos, V. Bunichev, E. Busato, L. Christofek, B. Clement, L.V. Dudko, T. Gadfort, A. Garcia-Bellido, G. Gaudio, D. Gele, P. Gutierrez, A.P. Heinson, S. Jabeen, S. Jain, A. Juste, D. Kau, M. Kopal, J. Mitrevski, J. Parsons, P.M. Perea, E. Perez, H.B. Prosper, A. Quadt, V.I. Rud, R. Schwienhorst, M. Strauss, B. Vachon, M. Warsinsky, G. Watts

E-mail conveners: Ann Heinson and Reinhard Schwienhorst

Abstract We perform a search for single top quarks in two production modes, s-channel (tb) and t-channel (tqb), separately and combined. The search is performed in the electron+jets and muon+jets decay channels, with either a soft-muon tagged jet, a secondary-vertex tagged jet, or a jet-lifetime-probability tagged jet to indicate the presence of a b-jet and thus improve the signal-to-background ratio. We use between 156 and 169 pb^-1 of Run II data, depending on the analysis channel, collected between August 2002 and September 2003. We do not find a statistically significant evidence for a single top signal and therefore set 95% confidence level upper limits on the single top production cross section. The resulting 95% confidence level upper limits on the production cross sections are 19 pb (s-channel), 25 pb (t-channel), and 23 pb (s+t channels).


Description of the analysis Read the conference note for Summer 2004. Analysis flow

Distributions of the number of good jets, the transverse mass of the W boson, and the scalar sum of the transverse energy of the electron, neutrino, and two highest-ET jets, for the electron and muon channel combined for the different background sources. The upper row shows the plots for the combination of JLIP and SLT, the lower row for the combination of SVT and SLT.