The Particle Physics Playbook Konstantin Matchev This talk

The Particle Physics Playbook Konstantin Matchev

This talk will not contain • Predictions of what new physics CDF might discover • The latest new physics models – See talks from LHC conference at Santa Barbara • The latest advances in NLO calculations – See talks from LHC conference at Santa Barbara – Come to F. Petriello’s talk on Wednesday morning • The model I have recently been working on – But in case you are interested: UMSSM = NMSSM + U(1) + N + exotica Lee, KM, Wang 2007 • Interesting features of UMSSM – – Z’ gauge boson and Z’-ino neutralino Scalar LSP: right-handed sneutrino dark matter Lee, KM, Nasri 2007 Te. V scale colored exotics Kang, Langacker, Nelson 2007 Z 3 discrete symmetries • B 3 (leptophobic Z’), L 3, M 3 – R-parity violation – Stable proton Luhn, Lee, KM 2007

This talk will contain • Jokes • Homework assignments • General classification of new physics signatures – Bump hunting – Bean counting • Review of (some) existing techniques for precision measurements at hadron colliders – Mass measurements – Spin measurements • Opportunities to do such measurements with existing Tevatron data • The discussion will be signature-based and largely model-independent • Useful “theorems”

What do we do for a living? • Look for new particles. How? - Full reconstruction (bump hunting) - Backgrounds can be measured from data - Easy to do mass, width measurements - More likely to be done with early data - Excess of events (bean counting) - Prone to systematic errors - Difficult to measure particle properties - Less likely to be done with early data Run II V. Shary CALOR 04 • It is worth thinking about bump hunts first! • It is possible to give an exhaustive and systematic classification of all resonance searches

Classification of resonance searches • How many resonances per event? (1 or 2) • How many objects does the resonance decay to? (2, 3, 4, …) • What are those objects? Note the absence of a “Missing energy calorimeter”

List of all di-object resonances m e g jet b t n m Z’ e g Z’ jet b LQ LQ n ‘Z’, ‘t’, ‘W’… W’ W’ h Z’ h • The scheme can be generalized to – three body decays etc. – pair-production etc. t LQ LQ h W’ -

More complicated topologies • A single resonance decaying to 3 objects (inclusive) • Pair production of resonances • Such searches are very model-independent • To summarize - just ask: – How many new resonances are present in each event? – What did each one decay to?

Homework • (Warm-up exercise) Classify all existing CDF new physics (and Higgs) searches according to this scheme. • Notice if there any remaining empty slots. Can you think of any reason why such a resonance should not exist? – If “yes”, report to me and/or the Theory Group – If “no”, then proceed to next step. • Think of a model where such a resonance would exist. (Ask your theory friends for help. ) • Is there a good reason why CDF is not looking for such a resonance? – If “Yes”, go back to previous step. – If “No”, proceed. • Is D 0 looking for it? If yes, talk to D 0. If no, proceed. • Are ATLAS/CMS going to look for it? If yes, talk to them. If no, proceed. • If you got here, talk to your physics coordinator.

Useful Theorems • Hinchliffe’s theorem: If the title of a paper is in the form of a “Yes/No” question, the answer is always “No” – Corollary: “If the abstract of the paper claims the answer is “Yes”, the paper is wrong and should be rejected” • Folk theorem: If you ask a theorist a question starting with “Is it possible to have a model where [I get signature X]? ” the answer is always “Yes” – Exception: Signature X violates some fundamental conservation law (e. g. charge conservation, Lorentz invariance etc. ) – Corollary: CDF should be on the lookout for allowed signatures. • Some “easy” examples – em resonance – trilepton resonance

SUSY and R-parity Violation • What is R-parity? – SM particles: +1 – Superpartners: -1 • Who needs R-parity? – Proton decay – Dark matter • What if R-parity was violated? – Superpartners will still decay down to the LSP – The LSP will decay to SM particles (resonance? ) – The LSP does not have to be neutral(ino)!

R-parity Violation • Baryon number violation: WBV = lijk Ui D[j Dk] • Lepton number violation: WLV = lijk Li Qj Dk + lijk L[i Lj] Ek

Signatures of R-parity Violation LSP UDD LQD LLE c 0 3 j ljj, njj lln gluino 3 j ljj, njj jjlln squark 2 j lj jlln slepton ljjj 2 j ln sneutrino njj 2 j ll chargino* 3 j ljj, njj 3 l • 2 LSP’s per event, large cross-sections • The leptons may be different flavor

Midpoint summary • Look for all possible resonances • R-parity violation: SUSY under the lamppost – Large rates from squark/gluino production – Resonances from LSP decays – Hard leptons if LV • LQD, LLE

Missing energy signatures • • Motivated by the dark matter argument Inevitable model dependence No resonances Follow the general classification: – How long was the cascade? – What were the emitted SM particles? • What can we measure? Mass? Spin?

Missing energy signatures a b C B a A b • Can be extended to longer cascades • Two such cascades per event • Repeat the previous homework • Can we measure the mass/spin of A, B? m e NA W W m e g jet b t t t g jet b t W t

Mass measurements • Single semi-invisibly decaying particle e W n • Use the transverse mass distribution

Mass measurements • A pair of semi-invisibly decaying particles e W W n n m Lester, Summers 99 Barr, Lester, Stephens 03 • Use the “stransverse” mass (MT 2) • This formula is valid for mn=0. Kong, KM

Homework • Use MT 2 to measure the W mass in dilepton W pair events • Use MT 2 to measure the top quark mass in dilepton tt-bar events Cho, Choi, Kim, Park 2008

SUSY or UED? • Folk theorem: Any signals of new physics can be explained with some SUSY model • A more recent theorem Any SUSY signature can be faked by some UED or Little Higgs model – Corollary: Any signal of new physics can have alternative explanations unless we can measure spins • KK masses at one-loop Cheng, KM, Schmaltz 2002 Only the LKP is stable. The LKP is neutral (DM!)

Model discrimination/Spin determination Battaglia, Datta, De. Roeck, Kong, KM 05 • What is the nature of A, B, C, D? – Find $N, 000, 000 and build an ILC – Find the momentum of A, fully reconstruct the event – Study m 2 distributions of visible particles Athanasiou et al 06, Kilic, Wang, Yavin 07, Csaki, Heinonen, Perelstein 07, S. Thomas (KITP) • The distributions depend on – – Spins of A, B, C, D Masses of A, B, C, D Chirality of couplings Initial state (particles vs antiparticles) • Most spin studies compare two sets of spin assignments, but fix everything else • That is not a true measurement of the spin Cheng, Engelhardt, Gunion, Han, Mc. Elrath 08

“SUSY” vs “UED” • Mass spectrum {A, B, C, D}={1000, 600, 420, 210} Ge. V Burns, Kong, KM, Park 08

Homework • Consider dilepton WW events and try to discriminate the following alternatives: – – W pair -> 2 leptons + 2 neutrinos, Slepton pair -> 2 leptons + 2 neutralinos Chargino pair -> 2 leptons + 2 sneutrinos KK lepton pair -> 2 leptons + 2 KK photons • Consider dilepton top pair events and try to discriminate the following alternatives – – t -> b W -> b+lepton+neutrino t -> b H+ -> b+lepton+neutrino stop -> b chargino -> b+lepton+sneutrino KK top -> b KK W -> b+lepton+KK neutrino

A positive note • Clean multilepton + MET events in SUSY hino l. L wino l. R – 3 leptons: gold plated mode – 4 leptons: platinum plated? – 8 leptons: ? ? ? • What is the max number of leptons? q. L q l wino l. L l bino q. L l l l. R hino bino

Advertisement • Check out the MC 4 BSM workshops – Fermilab 2006 – Princeton 2007 – CERN 2008

Summary • Think about model-independent signature based searches. – Resonances – Missing energy • Ask for theory model later. • Think of ways to test the proposed methods for precision measurements at the LHC (masses, spins etc. ) with existing Tevatron data. • Do the homework.

BACKUP SLIDES

How do we know LHC will find anything new or interesting? • The X 7 argument • Where is the Higgs?