People: Priscilla Pani, Giacomo Polesello, Amit Chakraborty, Björn Herrmann, Benjamin Fuks, Mihoko Nojiri, Abishek Iyer, Ramona Gröber

Email: priscilla.pani@cern.ch, giacomo.polesello@cern.ch, herrmann@lapth.cnrs.fr, amit@post.kek.jp, fuks@lpthe.jussieu.fr, nojiri@post.kek.jp, abhishek@theory.tifr.res.in, ramona.groeber@durham.ac.uk

• Investigate QFV signature: pp → t j ETmiss
• Start by implementing a simplified model, then try to move on to more realistic case.

We start by investigating a simplified model setup as follows. We complement the SM by a right-handed scharm (scR) and stop (stR).

In the gauge eigenbasis, the two-squark system is parametrized with the three parameters:

• Mst (stop mass parameter),
• Msc (scharm mass parameter),
• Mstc (mixing parameter).

After diagonalisation, in the mass eigenbasis, the three physical parameters are:

• Msq1 (lighter squark),
• Msq2 (heavier squark),
• theta (mixing angle),

such that sq1 = ct*scR + st*St (and the corresponding relation for the second squark state sq2).

In addition, we add to the model a gluino (go), with the appropriate SUSY mixings (so that it will contribute to the various production process) and a bino (chi) that will allow both squarks to decay. The corresponding mass parameters are

• Mchi (neutralino mass),
• Mgo (gluino mass).

The FeynRules model file is available here, and the corresponding UFO there. Do not forget, in madgraph, to load the model as

 import model stop-scharm_UFO -modelname 

and that the neutralino is called chi (and not n1).

1. Compute diagonal production cross-sections (at LO): function of mSq1 and mSq2, but independent of thSq.

2. Compute non-diagonal production cross-sections (at LO): function of mSq1, mSq2, and thSq. Evaluate, e.g., for thSq=(0, pi/4, pi/2) and mGl=3 TeV, and check importance w.r.t. diagonal production.

3. Compute branching ratios of Sq1 and Sq2 into t+N1 and into c+N1: function of mSq1, mSq2, thSq, mN1.

4. From the above, deduce cross-sections pp → t t ETmiss, pp → c c ETmiss, pp → t c ETmiss: functions of mSq1, mSq2, thSq, mN1. Make sure to seperate contributions from different subchannels, since this information is necessary to determine the experimental acceptance!

5. Compute the above signal cross-sections in the full model (i.e. with 4×4 mixing) and use the obtained acceptances to deduce the limits.

• “Squark and gaugino hadroproduction and decays in non-minimal flavour violating supersymmetry” (arXiv)
• “Impact of squark generation mixing on the search for squarks decaying into fermions at LHC”, (arXiv)
• “General squark flavour mixing: constraints, phenomenology and benchmarks” (arXiv)
• “Gluino Meets Flavored Naturalness” (arXiv)
• “Light stop decays” (arXiv)
• “Light stop decays into WbN1 near the kinematic threshold” (arXiv)