mSUGRA SUSY Searches at the LHC Why use mSUGRA and what signals does it give ? Detector requirements. SUSY discovery (production via strong interactions): Squarks & gluinos. Next-to-lightest neutralino. SUSY parameter determination: From Drell-Yan production cross-sections (gauginos & sleptons) Sparticle masses (neutralinos, squarks & gluinos) Conclusions Ian Tomalin 15/01/2019

Why use mSUGRA ? Why not just use the MSSM ? Particles: SM ones + 5 Higgs Sparticles: Spin 0 partners of SM fermions: qL,qR,lL,lR,nL Spin 1/2 partners of bosons/Higgs: c10,c20,c30,c40,c1±,c2±, g Nice theory, but 124 free parameters ! Ian Tomalin 15/01/2019

Why use mSUGRA ? mSUGRA (minimal Supergravity) Favourite SUSY theory for LHC studies. (Peter will discuss alternatives). Only 5 parameters (+ SM ones): m_0 (Scalar mass at GUT scale) ~ Squark & Slepton masses. m_1/2 (Gaugino mass at GUT scale) ~ Gaugino & gluino masses. tan(b) (VEV ratio of 2 Higgs doublets). A_0 (Higgs-fermion-antifermion coupling) sign(m) (Higgsino mixing parameter) Ian Tomalin 15/01/2019

mSUGRA Characteristics m_1/2 (GeV) lR mass contours N.B. lR mass is approximately m_0. m_0 (GeV) Ian Tomalin 15/01/2019

mSUGRA Signals R-parity: SUSY particles pair-produced c10 is stable (so missing ET). Mass (q, g) > mass (t) > mass ( l, c) SUSY production: Dominated by q & g (strong interaction) - up to 100M/year. Some l & c from Drell-Yan (EW interaction) ~ 10K/year. SUSY decays: Give ET(miss), many (b-)jets, leptons. Ian Tomalin 15/01/2019

mSUGRA Signals s(q) >> s(g) q ® q’ c ; c20 ® l+ l- 1 2 s(q) >> s(g) q ® q’ c ; c20 ® l+ l- s(q) ~ s(g) q ® q’ c ; g ® t t; c20 ® c10 h/Z m_1/2 (TeV) ~ mass c & g s(q) << s(g) g ® t t; c20 ® c10 h/Z s(q) << s(g) g ® c10 t t; c20 ® c10 l+ l- m_0 (TeV) ~ mass q & l Ian Tomalin 15/01/2019

Detector Requirements Calorimeter coverage for |h| < 5 (i.e. q > 10): Needed for good ET(miss) resolution. Needed to identify Drell-Yan events - with jet veto. Tracker: To identify b jets. Prove leptons are isolated. Measure lepton momenta Ian Tomalin 15/01/2019

Detector Requirements Measured Et(miss) in events with no missing energy. Ian Tomalin 15/01/2019

SUSY Discovery - Squarks and Gluinos Expect up to 100M q and g per year ! Can discover in days ! Signatures: ET(miss), many (b-)jets, leptons Selection cuts depend on m_0 and m_1/2 … SM Backgrounds: t t, W/Z + jets. Huge SUSY cross-section means Signal/Background ~ 1. By end of LHC life, explore q and g masses up to ~3 TeV. Ian Tomalin 15/01/2019

SUSY Discovery - Squarks and Gluinos Signal and background for events with two like-charge isolated leptons. N_jet Pt (lepton) Pt (jet) Et (miss) Et (sum) Ian Tomalin 15/01/2019

SUSY Discovery - Squarks and Gluinos m_1/2 (TeV) ~ mass c & g m_0 (TeV) ~ mass q & l 1 2 1 lepton 2 SS leptons 3 leptons 2 OS leptons c10 = dark matter Explored region after 1st LHC year. Various final states help constrain SUSY. Easily cover region where c10 could be dark matter. Ian Tomalin 15/01/2019

SUSY Discovery Next-To-Lightest Neutralino q and g often decay to c20. c20 ® c10 l+ l- Mass (l+l-) has sharp upper threshold: -- Clear signal for SUSY -- Measures m_1/2 !! If decay proceeds via slepton, also measures m_0. 1 months running ! Ian Tomalin 15/01/2019

SUSY Discovery Next-To-Lightest Neutralino m_0 (TeV) ~ mass q & l 1 m_1/2 (TeV) ~ mass c & g 0.5 c20 ® lL+ l- c20 ® lR+ l- c20 ® c10 l+ l- Reach after 1 year’s high luminosity running. Ian Tomalin 15/01/2019

Constraining SUSY with Cross-Sections Measure q & g rate to various final states (1, 2, 3 leptons …) (Tend to decrease with increasing m_0 and m_1/2.) Measure Drell-Yan (EW) production rates of: c1+ c20 (3 lepton final state) l+ l- (2 lepton final state) (Must use jet-veto to suppress q & g SUSY background. Need large luminosity.) Ian Tomalin 15/01/2019

Constraining SUSY with Sparticle Masses Providing c20 ® c10 l+ l- then: Can measure m_1/2 using maximum l+l- mass seen in c20 ® c10 l+ l- . Can also measure m_0, if c20 decays via slepton. At maximum l+l- mass, know c20 momentum: P(c20) = P( l+l- ) .[M(c20) /M( l+l- ) ] where M(c20) estimated from m_0. If qL ® qc20 or g ® qq ® qqc20 , can then determine qL and g mass. Ian Tomalin 15/01/2019

Conclusions Many studies use mSUGRA, as better constrained than MSSM. Detectors must find ET(miss), (b-)jets and isolated leptons. Need excellent solid angle coverage. SUSY may be discovered within days of LHC start-up via production of squarks and gluinos. .c20 ® c10 l+ l- decays could determine sparticle masses. Together with cross-section measurements, this helps constrain SUSY. Ian Tomalin 15/01/2019