1 / 23

Managing Multilepton Topologies: the Tau Trouble & a Concrete Proposal

Managing Multilepton Topologies: the Tau Trouble & a Concrete Proposal. Sunil Somalwar with Sourabh Dube, Julian Glatzer, Richard Gray, Alex Sood and Scott Thomas (Rutgers) Characterization of New Physics @LHC Workshop CERN Nov 5-6, 2010. Rutgers University, New Brunswick, NJ.

odina
Télécharger la présentation

Managing Multilepton Topologies: the Tau Trouble & a Concrete Proposal

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Managing Multilepton Topologies: the Tau Trouble& a Concrete Proposal • Sunil Somalwar • with Sourabh Dube, Julian Glatzer, Richard Gray, Alex Sood and Scott Thomas • (Rutgers) • Characterization of New Physics @LHC Workshop • CERN Nov 5-6, 2010 Rutgers University, New Brunswick, NJ Sunil Somalwar

  2. Outline • Multilepton complications & an attempt at making CDF trilepton results model-independent • An LHC proposal from the lessons learnt: • -- exclusive “theory” channels • Practical realities from working experience • “Addressing the Multi-Channel Inverse Problem at High Energy Colliders: A Model Independent Approach to the Search for New Physics with Trileptons” • Sourabh Dube, Julian Glatzer, Sunil Somalwar, Alexander Sood, Scott Thomas • arXiv:0808.1605 • (Scott Thomas yesterday) Rutgers University, New Brunswick, NJ Sunil Somalwar

  3. “Channels” : Theory vsExpt • For experimentalists: • Number of leptons 3, 4 or more • Flavor of leptons  e or mu • Lepton Reconstruction • High Quality: Tight e or mu (could be from a tau) • Medium Quality: Loose e/m, 1-prong t as isolated track • Low Quality: 3-prong tau’s, possibly jumbled up tau’s • For Theorists: • Number of leptons • Flavor of (parent) leptons (tau in particular) Rutgers University, New Brunswick, NJ Sunil Somalwar

  4. Expt. Channels Give Observed Signals CDF 2fb-1 Trilepton PRL 101, 251801 (2008) Exclusive channels: (t – tight lepton, l – loose lepton, T – isolated track) • Observed minus expected  Nobserved signal in each channel • Limit or measurement – No distinction. • No Model so far (although signal now “observed”.) Rutgers University, New Brunswick, NJ Sunil Somalwar

  5. Now Need A Model Model for the “observed” signal (for PRL purposes…) (mSUGRA) PRL 101, 251801 (2008). t – tight lepton, l – loose lepton, T – (isolated) Track Rutgers University, New Brunswick, NJ Sunil Somalwar

  6. Expt.Channels   PRL(via a Rather Messy Scenario)  sigma*BR vs Model Expectations Contours (1st mSUGRA) tan(beta) =3. CDF 2fb-1 Trilepton PRL 101, 251801 (2008) Rutgers University, New Brunswick, NJ Sunil Somalwar

  7. Not a Pretty Scene Tom Banks: “Nice work, Sunil, but we already know that mSUGRA does not describe Nature.” Rutgers University, New Brunswick, NJ Sunil Somalwar

  8. The Question • Regardless of the motivation behind cuts, the analysis is done. • N(observed signal) /Luminosity written in stone (in many exptchannels). • How to map the experimental result onto theory channels? • Theory tau’s show up as e, mu, clean isolated tracks, or as • dirty pencil jets. • Experimental acceptance is model dependent (specific topology). • Clean acceptance: kinematics: pt, eta, phi, met, angles.. • Dirty acceptance: Isolation, resolution, tails, pileup… “Just show sigma*BR. Why do you need models?” Rutgers University, New Brunswick, NJ Sunil Somalwar

  9. What We Did After CDF Trileptons Experimental [σB] is model-dependent because of acceptance. N : Observed signal (excess over SM in several experimental channels) L: Luminosity A: Total acceptance = Clean A (kinematic) times Dirty A (isolation etc) Stay in the topology but factorize: Factorize out the “theory” channels 0 t: (e/m) (e/m) (e/m) 1 t: (e/m)(e/m)t2 t: (e/m)tt3 t: ttt • Provide: [σB]0τ, [σB]1τ, [σB]2τ, and [σB]3τ,where, • [σB]0τ = N/LA0τ etc • Same observed signal N is used four times. The topology under consideration is split into four sub-topologies AT THE GENERATOR LEVEL. • e/mu go together and are fine with the combined treatment. • No approximations so far. Rutgers University, New Brunswick, NJ Sunil Somalwar

  10. How does it help? The signal is spread across four t channels, and not always in a simple way. • Rearrange: But, [σB]i = N/Lai, so Rutgers University, New Brunswick, NJ Sunil Somalwar

  11. How does it help? Run a topology 4 times (with generator level cuts) through analysis, calculate acceptances & publish [σB]0τ, [σB]1τ, [σB]2τ, & [σB]3τ. A theorist has her own BR’s (=Bi) (Maybe it is a different tan(beta)) Use the equation to combine the experiment and theory to get sXM (Experimentally measured cross section for the theorist’s model.) No approximations so far and we took care of the branching ratios. Branching ratios just an example.  We mapped the experimental result onto theory channels. (Basis or eigenchannels that can be recombined with weights.) Rutgers University, New Brunswick, NJ Sunil Somalwar

  12. An Example: Experimental Side • Luminosity = 0.1 fb-1, SM expectation=6, observed=9 • Observed signal = 3 •  N/L = (3)/(0.1fb-1) = 30fb [=(σB)A ] • Pick the topology. It has four exclusive “theory” channels. Get acceptances, selecting the channels at generator level. • 0 t: (e/m) (e/m) (e/m) (generator level) : Full acceptance A0= 11% • 1 t: (e/m)(e/m)t A1= 5% • 2 t: (e/m)tt A2= 3% • 3 t: ttt A3= 1.4% •  [σB]0= (N/L)/A0 = (30fb)/ (11%) = 0.27 pb • [σB]1= (N/L)/A0 = (30fb)/ (5%) = 0.6 pb • [σB]2= (N/L)/A0 = (30fb)/ (3%) = 1.0 pb • [σB]3= (N/L)/A0 = (30fb)/(1.4%) = 2.1 pb • Publish [σB]0, [σB]1, [σB]2, and[σB]3 . Rutgers University, New Brunswick, NJ Sunil Somalwar

  13. Example (contd): Theorist Side Theorist 1: tan(beta) = 2 etc, has s= 1.25 pb & BR’s B0=20%, B1=B2=B3=0 (1/sXM) = (20%/0.27pb) + 0 + 0 + 0  sXM = 1.35 pb Compare to stheory = 1.25 pb (Consistent) Theorist 2: tan(beta) = 8 etc, has s= 5 pb & BR’s B0=10%, B1=30%, B2=30%, B3=20% (1/sXM) = (10%/0.27pb) + (30%/0.6pb) + (30%/1.0pb) + (20%/2.1pb)  sXM = 0.8 pb Compare to stheory = 5 pb (Ruled out) Rutgers University, New Brunswick, NJ Sunil Somalwar

  14. Towards Model-independence • Part A : Exclusive theory channels • Define (experimental) channels, selection, SM expectations, N(Obs Signal), full acceptance (clean and dirty) for theory channels, and publish (for a given topology): • [σB]i’s for exclusive theory channels. • A spreadsheet utility for combining [σB]i‘s and theory BR’s. • Part B: Simplify/generalize topology • No general solution, approximations and scatter-shot at best. • Cover as many topologies as possible (We didn’t, but LHC can.) • [σB]i’sget extra mileage out of each topology. • The emphasis here is on Part A: [σB]i’s for exclusive theory channels. • Our topology efforts were rudimentary (but worked out alright.) Rutgers University, New Brunswick, NJ Sunil Somalwar

  15. mSUGRA  Simple Topology Approximations begin  Having a variety of topologies will be extremely useful. Had to do some underhanded things at the Tevatron  It is great that we are doing it in an organized/legal fashion @LHC (Thank you, organizers!) Here is the simplified model we used for CDF trileptons: • Three mass parameters • M (Lowest state mass) • ΔM1 (Upper minus • intermediate mass) • ΔM2: (Upper minus • lowest state mass) Rutgers University, New Brunswick, NJ Sunil Somalwar

  16. A Simple Topology Parameterization Rutgers University, New Brunswick, NJ (M = lowest, ΔM1 =upper – middle, ΔM2: upper – lowest) Dependence on M factors out: fi(M) No intermediate particle case: [σB]i)-1 = fi(M) * gi(ΔM2) One intermediate particle case: [σB]i)-1 = fi(M)*hi(ΔM1,ΔM2) Taylor expansions: fi(M) = 1 + a1(M) + a2(M)2 gi(ΔM2) = b0 + b1(ΔM2) + b2(ΔM2)2 hi(ΔM1,ΔM2) = c0 + c1(ΔM2) + d1(ΔM1) + c2(ΔM2)2 + d2(ΔM1)2 + e2(ΔM1*ΔM2) Sunil Somalwar

  17. A Simple Topology Parameterization f0(M) An Excel spreadsheet at: http://www.physics.rutgers.edu/pub-archive/0901 Good to 20-30% in the validity range Rutgers University, New Brunswick, NJ (M = lowest, ΔM1 = upper–middle, ΔM2: upper–lowest) [σB]i)-1 = fi(M) * gi(ΔM2) or fi(M)*hi(ΔM1,ΔM2) Sunil Somalwar

  18. CDF Published vs “Model-Independent”  CDF arXiv:0808.1605 & parameterized simplified topology Rutgers University, New Brunswick, NJ Sunil Somalwar

  19. Turning to LHC Scott Thomas and Richard Gray Also, Sanjay Padhi earlier. More complicated, but the exclusive theory channel approach, coupled with (possibly parameterized) simplified topology approach, should work. Rutgers University, New Brunswick, NJ Sunil Somalwar

  20. A Concrete Proposal for Disseminating Results • THEORISTS • Provide topologies (and sub-topologies).Identify exclusive channels for each topology (start with Feynman diagrams for subtopologies, or generator level jets, met, # leptons… exclusive signatures) • COMMON • SLHA files, possibly LHE. • Generation Level Kinematic (Clean) Acceptances (pt, eta, met, angles…) • EXPERIMENTALISTS • (experimental) channels, selection, SM expectations, N(Obs Signal), • full acceptances (clean and dirty) for theory channels, and publish • Publish N(Obs Signal)/L = (sBA) (very little effort) (Scott) • [σB]i’sfor exclusive theory channels. • Generation-level clean acceptances (see Common above). • A spreadsheet utility for combining [σB]i’sand theory BR’s. Rutgers University, New Brunswick, NJ Sunil Somalwar

  21. How will a theorist use the results? • Back-of-the-envelope Theorists • Identify a published topology that is closest to your topology • Input BR’s into the spreadsheet utility • Compare theory and experimental cross section • Enterprising (Simulation-Savvy) Theorists • Run on published (simple) topologies • SLHA files  Events  Generator level cuts  Verify the experimental values of Clean Acceptance • Normalize to experiment: Conclude the dirty acceptance (resolution, isolation etc) and use it as a correction factor • Switch to topology of interest, not necessarily a simple one. Rutgers University, New Brunswick, NJ Sunil Somalwar

  22. Exclusive Channels: an Ambitious Example • At the generator level, split the entire SUSY signal of a model • 5 or more leptons (e, mu and tau’s), then • 4 leptons (0,1,2,3,4 tau’s), then • 3 leptons (0,1,2,3 tau’s), then • … • Same-sign e/mu’s (additional leptons too soft to be above.), then • … • Monolepton • Jets without leptons • (Works short of interference effects) • MET, HT, # jets used along the way to build up signal/background • Also: Define sub-channels just for individual lepton/jet searches • Complicated color chains: Each chain a channel (no interference) • ATLAS and CMS (with theorists) can identify these channels and then each generate channel-tagged MC (CTMC) samples. Multiple analysis groups within both ATLAS and CMS can then produce combinable results in form of exclusive (sBi)’s. Rutgers University, New Brunswick, NJ Sunil Somalwar

  23. Conclusions • Identify exclusive channels in a model at the generator level. Channel-tagged MC (CTMC) will identify (simpler) constituent topologies within a complicated model and track them all the way through publication and follow-up pheno analyses. • Get much more mileage out of a model/topology by providing sigma*Br’ s for exclusive internal channels. • Doing so makes it easy to combine pieces within and between experiments. • At the very least, easily factorize branching ratios from the multidimensional parameter space for models. • Experiments will always have to deal with the dirty acceptance, but providing generator-level clean acceptance separately will allow enterprising theorists to tune their simulation tools better. • Unrelated: Organizing analyses within the experiment along exclusive (experimental) channels is advantageous. Rutgers University, New Brunswick, NJ Sunil Somalwar

More Related