1st generation Leptoquark Search

Plots shown by Jianming at LaThuile 98

The Preliminary Run 1b Analysis

We search for 1st generation pair-production of leptoquarks by looking for (1) events with 2 electrons and 2 jets, (2) events with 1 electron, missing transverse energy, and 2 jets, and 3) events with 2 acolinear jets and missing transverse energy. We search for 3rd generation charge 1/3 leptoquark pair production by looking for events with 2 b jets and missing transverse energy. The last search is the same as our STOP analysis.

Theoretical cross section plot showing vector LQ(Yang-Mills), scalar LQ at LO, scalar LQ at NLO and top cross sections versus mass
Scalar Leptoquarks
- eejj Channel
  - ST for data vs. Monte Carlo in integral and differential views.
  - Di-electron invarient mass peak: data vs. Monte Carlo
  - Optimization plot from RGSEARCH
  - HTe vs. HTj plots with the NN analysis contours
  - 3C Mass vs. ST and 3C mass only plots (from PRL)
  - Efficiency plot for the eejj ST based selection
  - Limit plot: eejj channel only
- enujj Channel
  - Efficiency plot for the enjj dM based selection
  - electron-MET transverse mass peak: data vs. Monte Carlo, no MTrans or dM cut
  - Limit plot: enjj channel only
- Combined Results
  - Beta vs. Mass limit plot: combined results
  - Confidence level vs. Mass: combined results
Vector Leptoquarks
- plot efficiency for 1st generation vector lq's versus mass
- plot Limits on vector 1st generation lq's

The Run 1a Analysis

This analysis is described in our 1st generation prl. The D0 experiment has published mass limits for electron type scalar leptoquarks using the data collected between 1992 and 1993. We reported a lower limit of 133 GeV/c^2 for the electron-type LQ if beta=1. The limit is reduced to 120 GeV/c^2 if beta=0.5.

1st generation prl Our published 1st generation paper

2nd generation prl Our published 2nd generation paper

Mass Lim vs Branching Frac, 1st Gen Scalar LQ (black and white)

ee mass This shows the measured distribution for the mass of the two electrons, along with a Monte Carlo prediction for the background distribution.
limit vs mass beta=1. the 95% C. L. upper limit on the leptoquark production cross section versus mass for beta=1, along with the theoretical calculation.

transverse mass dist This shows the distribution for the transverse mass calculated from the electron and the missing ET from a Monte Carlo prediction for the distribution from the backgrounds.

limit vs mass beta=0.5 The 95% C.L. upper limit on the leptoquark production cross section versus mass for beta=0.5, along with the theoretical calculation.

limit vs mass beta=0.0 The 95% C.L. upper limit on the leptoquark production cross section versus mass for beta=0.0, along with the theoretical calculation.