Difference: SusySubjet (17 vs. 18)

Revision 182006-08-10 - AreRaklev

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META TOPICPARENT	name="JonButterworth"

Identifying massive hadronic decays in SUSY decay chains.

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The SLHA file for John's \delta point has been generated with ISAJET 7.69, and SUSY decays added with SDecay 1.1. I checked the decays with the ones given by ISAJET and modulo small numerical differences they look the same. The file is attached. Also attached is the NLO cross sections for \delta as calculated with Prospino2.

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Plots for \delta have been produced and attached. As a first attempt we are looking for events were two W have been produced in chargino decays. The decay chain we are looking for is ~q_L -> q + ~chargino_1 -> q + W + ~neutralino_1.

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Plots for \delta have been produced and attached (NEW version as of 10.08.06). As a first attempt we are looking for events were two W have been produced in chargino decays. The decay chain we are looking for is ~q_L -> q + ~chargino_1 -> q + W + ~neutralino_1.

A short description of the plots follow:

Top left: Plot of pT of jets. Cut on pT>15 and |\eta| < 2.5. In red is shown jets matched to a parton level W (by the usual distance \Delta R < 0.1).

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Top right: Plot of jet mass m_W as given from jet algorithm. Same color coding. Cut on jet pT: 150 GeV < pT < 600 GeV.
Bottom left: Plot of jet log(pT*sqrt(y)). Same color coding. Cut on jet pT: 150 GeV < pT < 600 GeV. Cut on jet mass: 80 GeV < m_W < 90 GeV.

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Top right: Plot of jet mass m_W as given from jet algorithm. Same color coding. Cut on jet pT: 150 < pT < 600.
Bottom left: Plot of jet log(pT*sqrt(y)). Same color coding. Cut on jet pT: 150 < pT < 600. Cut on jet mass: 80 < m_W < 90.

Bottom right: Plot of invariant mass of w+jet system. We require two W's identified in each event from the cuts given above pluss a cut on separation scale: 1.3 < log(pT*sqrt(y)) < 2.0. The W candidates are combined with the two hardest jets in the event. In red (signal) events with two decays of the type mentioned above.

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Note that the three first plots have been normalized, and the cuts have been added

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Note that the three first plots have been normalized, and the cuts accumulated through the plots, which was not done in the first version. From the distributions of jet pT and mass, cuts look to be potentially very effective. However, in the log(pT*sqrt(y)) distribution the W-tagged jets have almost the same distribution as other jets, with only a slight excess just below log(pT*sqrt(y))=2. As a result the cut on separation scale is not very effective, and in the invariant mass distribution we see that while the signal plot (red) has roughly the expected endpoints, one can show analytically that for the \delta masses we should have 247 < m_{qW} < 1272, it is burried in SUSY background.

As you can see there is no longer a top peak as in the first version, so this is no longer a problem. There are still too many background jets, and rather surprisingly the separation scale cut does not work very well. I

We have discrimination between the W's and other jets as seen from the first three plots, but the invariant mass plot shows there are too many W candidates around after cuts. Note the a part of the problem is the copious production of top quarks in this model, which can be seen as peaks in the invariant mass plot. I'm still working on the numbers for how efficient the cuts are and how much of the problem is caused by the real W's produced in other decays, and how much is being faked by other jets.

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delta.ps: Som start-up plots for \delta

META FILEATTACHMENT	attr="" autoattached="1" comment="Cross sections at NLO for \delta calculated with Prospino2" date="1153423812" name="delta.xsec" path="delta.xsec" size="10409" user="Main.AreRaklev" version=""

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META FILEATTACHMENT	attachment="delta.ps" attr="" comment="Som start-up plots for \delta" date="1155220072" name="delta.ps" path="delta.ps" size="29727" stream="delta.ps" user="Main.AreRaklev" version="0"

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META FILEATTACHMENT	attr="" autoattached="1" comment="Som start-up plots for \delta" date="1155220073" name="delta.ps" path="delta.ps" size="29727" user="Main.AreRaklev" version=""

META FILEATTACHMENT	attr="" autoattached="1" comment="SLHA file for the \delta benchmark" date="1153400562" name="delta_slha.dat" path="delta_slha.dat" size="46913" user="Main.AreRaklev" version=""

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