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Probing 23% of the Universe at the Large Hadron Collider

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Probing 23% of the Universe at the Large Hadron Collider Probing 23% of the Universe at the Large Hadron Collider Will Flanagan1 Advisor: Dr Teruki Kamon2 In close collaboration with Bhaskar Dutta2, Alfredo Gurrola2, Nikolay Kolev3, Tom Crockett2, Michael VanDyke2, and Abram Krislock2 1University of Colorado at Boulder, Cyclotron REU Program 2Texas A&M University 3University of Regina Introduction What is cosmologically significant about ‘focus Analysis With recent astronomical measurements, point’? We first decide which events we want to look for. χ~0 ~0 we know that 23% of the Universe is The 1is allowed to annihilate with itself since it is Since χ 1 is undetectable (otherwise it wouldn’t be ‘dark composed of dark matter, whose origin is its own antimatter particle. The χ~ 0 -χ~0 annihilation matter’!), we look for events with a 1 1 Red – Jet distribution unknown. Supersymmetry (SUSY), a leading cross section is typically too small (predicting a relic after MET cut large amount of missing transverse theory in particle physics, provides us with a cold dark χ~0 Z channel dark matter density that is too energy. Also, due to the nature of 1 u- matter candidate, the lightest supersymmetric particle Z0 large). The small µ of focus these decays (shown below) we also χ~0 (LSP). SUSY particles, including the LSP, can be 1 u point x require two energetic jets. 2 f 1 Ω ~0 ~h dx created at the Large Hadron Collider (LHC) at CERN. allows for a larger annihilation χ1 ∫ 0 σ v { ann g~ 2 energetic jets + 2 leptons We perform a systematic study to characterize the cross section for our dark 0.23 698 u- + MET 2 g~ SUSY signals in the "focus point" region, one of a few matter candidate by opening πα ~ u - σ annv = 2 u l cosmologically-allowed parameter regions in our SUSY up the ‘Z channel’ (pictured 321 8M χ~0 l+ 0.9 pb 2 ~+ model. We also present a above). l χ~0 u 1 methodology for extracting the dark Methodology Furthermore, we can use matter signals at the LHC, and show We first perform a monte-carlo event simulation u- the invariant dilepton the accuracy to which we can ~0 0 Mass(GeV) χ ~ using a program called ISAJET. This program mass of 2,3 -> χ 1 decays measure the dark matter relic density and the SUSY calculates the outcomes of p-p collisions at LHC to probe the mass parameters. 0 ~0 energies. We then put this data through a detector 194 χ~ differences of the χ 1 to The ‘focus point’ is one of the few regions in the 2 ~0 ~0 level simulation, PGS4, to account for observational the χ 2 and the χ 3 . mSUGRA parameter space that is consistent with both errors such as track smearing. This data is then 103 ~0 cosmological constraints and particle physics χ 1 Dilepton analyzed in ROOT in order to hunt for observational edge observations. This region got its name from another signatures that can allow us to predict our input l+ l- parameter, µ, being ‘focused to a small value’. The parameters. Finally we determine a method of solving LSP (dark matter candidate) of focus point is the for our input parameters and use this information to Current/Future Work χ~0 neutralino-1, 1, a combination of the photino, bino, predict the dark matter relic density of our SUSY We are working on how we can disect the gluino and higgsino fermions. One particularly interesting trait model. ~0 mass from observables. We will then use these values of having a small µ in focus point is that the χ 1 has a ~0 very large higgsino component. This causes χ 1 to to calculate our mSUGRA parameters and the dark couple more strongly to heavier particles, favoring the matter relic density! In the mean time, we are testing the χ~0 top quark in hadronic decays to the 2 . efficiencies of our generation codes and analyzing our - t u- cuts for data analysis at the CMS. To be continued! ~ χ~0 » top favored ~ χ~0 g ~ 2 over other g ~ 2 t u Many thanks to the Cyclotron REU and TAMU HEP. t quarks!À u.
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