CDF Search based on ``Yet Another Extension of the Standard Model:
Oases in the Desert?', (authors: J.D. Bjorken,
S. Pakvasa, and S.F. Tuan)'
Sasha Paramonov, Collin Wolfe, Jason Tsui, Drew Fustin, Steve
Levy, Carla Pilcher, Henry Frisch, with lots of help from Arjun Menon
Brief General Introduction
This model has new heavy particles in the down sector: right-handed
ewk-singlet down (D,S,B; generically called Q) quarks, and
ewk-doublet heavy charged and neutral leptons (\nu_E, E, \nu_M, M,
\nu_T, T; generically called N and L). The heavy down particles
mix with the respective SM down sector.
We have implemented this model within a copy of the program
MadGraph.
MadGraph V3.0 outputs the helicities along with 4-vectors, an
essential ingredient as the couplings depend strongly on the
helicities. The Q (heavy quark) decays into W:Z,H (Higgs) in the
approximate ratios of 2:1:1. We use Fabio Maltoni's Decay program to decay the
W,Z, and Higgs to make the matrix element final files of
partons. These are then run through the CDF reconstruction and simulation.
Nitty Gritty of the Model: Couplings of the Q, N, and L to A,W,Z,
and H
Arjun Menon has translated the paper into currents so that we can read
off the couplings for the MadGraph code. We've made a table of the
couplings with the MadGraph conventions from Arjun's currents:
Couplings (Page 3 is the table; pp1,2 are
the MadGraph conventions. Substance by Arjun Menon) .
.Tex file of Couplings .
Production
The following plots show the cross-sections for quark-pair and lepton
pair production versus mass.
The masses are unknown, but the paper
suggests that the new down quarks may be two or three times
more massive than the new leptons. Two other plots have been produced
that scale the quark mass down by a factor of two or three in order to
be able to directly compare the lepton cross-section with the quark
cross-sections of quarks that are this factor more massive.
Plot of the cross-sections
at pbar-p collisions at root-s=1.96 TeV for pair-production of leptons
and quarks over a range of masses.
.
Same plot, but with the
quark masses scaled by one-half to allow comparison between the
cross-sections of leptons with quarks that are twice as
massive.
Same plot, but with the
quark masses scaled by one-third to allow comparison between the
cross-sections of leptons with quarks that are three times as
massive.
Final State Sigma times BR's and Kinematics
The Decay package in MadGraph decays the secondary particles tracking
the (all-important) helicities. This is still all at LO and parton
level; the output files are the ones fed to Pythia, CDFSIM, CDF
production, and ntupling.
Pt, eta, and helicity
distributions for the u-quark and the W- in QQ~ -> u u~ W- W+
production. For M_Q = 300 GeV, the total QQ crossection is 0.412
pb. The sigma times (BR)**2 for n QQ~ -> u u~ W- W+ is 0.103 pb.
Note that the longitudinal W's completely dominate at this mass (was
much more evenly distributed at M_Q= 175 GeV). Note also the high-Pt
W's.
Plots of Pt, eta, and helicity
distributions for the quarks and W's in QQ~ -> u u~ W- W for M_Q=300
GeV.
Plots of Pt, eta, and helicity
distributions for the secondaries from the W decays in QQ~ -> u u~ W-
W for M_Q=300 GeV.
The two scatter plots correspond to plots of the Pt of the e+ from W+
decay vs the Pt of the e- from W- decay (first plot), or the pt's of
the nu vs nubar, but summed over all decay modes of the two W's for statistics.
One can see that the I=+1/2 plot seems to have softer Pt spectra.
Last updated Feb 6, 2005; HJF