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DTSTART;TZID=America/Los_Angeles:20170112T160000
DTEND;TZID=America/Los_Angeles:20170112T170000
DTSTAMP:20260423T135432
CREATED:20161201T111821Z
LAST-MODIFIED:20161201T111821Z
UID:414-1484236800-1484240400@rpm.physics.lbl.gov
SUMMARY:Siyuan Sun (Harvard) "Gaining Sensitivity to New Physics with a Compressed Mass Spectra at the ATLAS Experiment"
DESCRIPTION:ABSTRACT\nThe ATLAS experiment at Large Hadron Collider (LHC) searches for experimental ev-\nidence of many new beyond the standard model physics at the TeV scale. As we collect\nmore data at the LHC we continue to extend our sensitivity to these new phenomenon\,\nparticularly probing increasingly more massive new particles. Despite this progress there\nare still regions of parameter space where constraints remain weak. One common cause of\nthis lack of sensitivity is because the new particle has a very small mass splitting between it\nand its decay products. The particle then has little energy left over to give momenta to its\ndecay products and the low momenta decay products are difficult to experimentally detect.\nThese regions of small mass splitting are called compressed regions. We are able to gain\nsensitivity to these difficult regions by searching for new particles produced in conjunction\nwith strong initial state radiation (ISR). The strong initial state radiation boosts the new\nparticle’s decay products and gives them momentum.\nIn this seminar\, I will cover in detail the search for the supersymmetric partner to the\ntop quark (stop) in the region when the stop and its decay products are nearly degenerate in\nmass. No searches prior to 2016 was sensitive to this region. We were able to exclude stops\nup to a mass of 425 GeV in this region with the 2015 and summer 2016 ATLAS dataset. I will\ndemonstrate a new and more accurate technique for identifying whole initial state radiation\nsystems instead of a single ISR jet. As the LHC provides more data and traditional search\nmethods rule out parameter space at higher masses\, it becomes more important that we also\ngain sensitivity to these compressed regions that are still unconstrained at low masses. I will\nshow that this initial state radiation identification technique is completely generalizable and\nuseful for many other searches that target small mass splittings.
URL:https://rpm.physics.lbl.gov/event/siyuan-sun-harvard-tba/
LOCATION:Zoom Talk\, 50A-5132\, Berkeley\, ca\, 94720
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