12 Mar 2004, KTH, Stockholm. Peter Skands Dept. of Theoretical High Energy Physics, Lund University LHC

Transcription

1 12 Mar 2004, KTH, Stockholm Peter Skands Dept. of Theoretical High Energy Physics, Lund University LHC Including how to: Save the proton from a Supersymmetric Death. Measure a Neutrino Angle at a Hadron Collider. See also W. Porod+PS, hep-ph/ T. Sjöstrand+PS, Nucl.Phys.B659:243(2003) PS, Eur.Phys.J.C23:173(2002) RPV LHC, P. Skands p.1/36

2 Overview 1. Quick SUSY intro. 2. SUSY and the proton. 3. R Parity Violation with Trilinear Terms. (a) Lepton Number Violation (@ LHC). (b) Baryon Number Violation (@ LHC). 4. Lepton Number Violation with Bilinear Terms. (a) a SUSY origin of masses? (b) Measuring a angle at a hadron collider? RPV LHC, P. Skands p.2/36

3 Quick SUSY Intro A brief look beyond the Standard Model... RPV LHC, P. Skands p.3/36

4 Supersymmetry. Could there be more space time symmetries? The Symmetries of Space and Time: Lorentz invariance, Translational invariance, Rotational invariance is that all? Coleman-Mandula Theorem All possible symmetries of the S matrix,phys.rev.159:1251(1967) YOU CAN T DO IT... it s too boring. RPV LHC, P. Skands p.4/36

5 Supersymmetry. Could there be more space time symmetries? The Symmetries of Space and Time: Lorentz invariance, Translational invariance, Rotational invariance is that all? Coleman-Mandula Theorem All possible symmetries of the S matrix,phys.rev.159:1251(1967) YOU CAN T DO IT... it s too boring. Haag-Lopuszanski-Sohnius Theorem: All possible generators of supersymmetries of the S matrix,nucl.phys.b88:257(1975) WITH SUPERSYMMETRIES it s not boring at all... RPV LHC, P. Skands p.4/36

6 So what is Supersymmetry? Could bosons and fermions be related? The generators of a supersymmetry, anti-commute: (and ), i.e. they are fermionic and relate particles of different spin: RPV LHC, P. Skands p.5/36

7 So what is Supersymmetry? Could bosons and fermions be related? The generators of a supersymmetry, anti-commute: (and ), i.e. they are fermionic and relate particles of different spin: If Nature incorporates supersymmetry, bosons and fermions should thus be intimately related. RPV LHC, P. Skands p.5/36

8 So what is Supersymmetry? SUPERSYMMETRY For every boson, there is a fermion For every fermion, there is a boson 6 leptons + 6 quarks S= photon + and + gluon S=1 Higgs S=0 RPV LHC, P. Skands p.6/36

9 So what is Supersymmetry? SUPERSYMMETRY For every boson, there is a fermion For every fermion, there is a boson 6 leptons + 6 quarks S= 2 6 sleptons squarks S= 0 photon + and + gluon S=1 photino + Winos and Zino + gluino S= Higgs S=0 Higgsino S= RPV LHC, P. Skands p.6/36

10 But what s the point? Supersymmetry. Why should Nature respect this weird symmetry? Instead of reducing the mess, we ve doubled the spectrum of physical states! It makes sense because: SUSY gives the largest possible space time symmetry. RPV LHC, P. Skands p.7/36

11 But what s the point? Supersymmetry. Why should Nature respect this weird symmetry? Instead of reducing the mess, we ve doubled the spectrum of physical states! It makes sense because: SUSY gives the largest possible space time symmetry. SUSY gives experimentalists something to look for. SUSY may solve the dark matter problem. RPV LHC, P. Skands p.7/36

12 But what s the point? Supersymmetry. Why should Nature respect this weird symmetry? Instead of reducing the mess, we ve doubled the spectrum of physical states! It makes sense because: SUSY gives the largest possible space time symmetry. SUSY gives experimentalists something to look for. SUSY may solve the dark matter problem. SUSY elegantly solves the hierarchy problem. RPV LHC, P. Skands p.7/36

13 + $ * ( ' & % 1 0 SUSY can solve the Hierarchy Problem Quantum corrections to the Higgs mass due to fermions: f "! h h GeV ' ) GeV # ) -./, EXTREMELY finetuned! (with RPV LHC, P. Skands p.8/36

14 % $ 1 0 SUSY can solve the Hierarchy Problem Quantum corrections to the Higgs mass due to (s) fermions: f h h 0 h h # ) -./, NOT finetuned! ( even with RPV LHC, P. Skands p.8/36

15 But what s the point? Supersymmetry. Why should Nature respect this weird symmetry? Instead of reducing the mess, we ve doubled the spectrum of physical states! It makes sense because: SUSY gives the largest possible space time symmetry. SUSY gives experimentalists something to look for. SUSY may solve the dark matter problem. SUSY elegantly solves the hierarchy problem. SUSY leads to natural Grand Unification. RPV LHC, P. Skands p.9/36

16 SUSY Leads to Grand Unification GUT s with only SM as underlying theory are ruled out, essentially from measurements of the weak mixing angle. GUT s with SUSY can do wonderful things: RPV LHC, P. Skands p.10/36

17 But what s the point? Supersymmetry. Why should Nature respect this weird symmetry? Instead of reducing the mess, we ve doubled the spectrum of physical states! It makes sense because: SUSY gives the largest possible space time symmetry. SUSY gives experimentalists something to look for. SUSY may solve the dark matter problem. SUSY elegantly solves the hierarchy problem. SUSY leads to natural Grand Unification. SUSY is the super in superstring theory. RPV LHC, P. Skands p.11/36

18 Overview 1. Quick SUSY intro. 2. SUSY and the proton. 3. R Parity Violation with Trilinear Terms. (a) Lepton Number Violation (@ LHC). (b) Baryon Number Violation (@ LHC). 4. Lepton Number Violation with Bilinear Terms. (a) a SUSY origin of masses? (b) Measuring a angle at a hadron collider? RPV LHC, P. Skands p.12/36

19 Aberdabei So SUSY is really popular, but... in any Supersymmetric extension of the Standard Model (SM), the first problem you have to deal with, is how to avoid rapid proton decay! RPV LHC, P. Skands p.13/36

20 ' % % BNV+LNV together is a bad cocktail! Write down all (renormalizable) terms consistent with SM gauge invariance and ( ) Supersymmetry RPV LHC, P. Skands p.14/36

21 ' % % 9 # + )% # ; 7! 9 # BNV+LNV together is a bad cocktail! Write down all (renormalizable) terms consistent with SM gauge invariance and ( ) Supersymmetry NOT INTERESTING NOW! $&%,, + )% # ' $(*)! "# ' 7 ) #, + /. - )% # : % " '=< >@? A # 0 % ' $(*) RPV LHC, P. Skands p.14/36

22 ' % % 9 # + )% # ; 7! 9 # BNV+LNV together is a bad cocktail! Write down all (renormalizable) terms consistent with SM gauge invariance and ( ) Supersymmetry NOT INTERESTING NOW! $&%,, + )% # ' $(*)! "# ' 7 ) #, + /. - )% # : % " '=< >@? A # 0 % ' $(*) RPV LHC, P. Skands p.14/36

23 ' % % 9 # + )% # ; 7! 9 # BNV+LNV together is a bad cocktail! Write down all (renormalizable) terms consistent with SM gauge invariance and ( ) Supersymmetry NOT INTERESTING NOW! $&%,, + )% # ' $(*)! "# ' 7 ) #, + /. - )% # : % " '=< >@? A # 0 % ' $(*) ' ) fast proton decay RPV LHC, P. Skands p.14/36

24 $ ' # What can be done? Start with naive, simple guesses: 1. Lepton Number is conserved? 2. Baryon Number is conserved? 3. Both are conserved ( -parity )? RPV LHC, P. Skands p.15/36

25 $ ' # ' ' % What can be done? Start with naive, simple guesses: 1. Lepton Number is conserved? 2. Baryon Number is conserved? 3. Both are conserved ( -parity )? -parity has interesting consequences: SM particles have and SUSY ones sparticles are born and killed by the pair... so sparticles from Big Bang decayed to LSP are still around? solution of dark matter problem in cosmology? But no deep theoretical motivation... RPV LHC, P. Skands p.15/36

26 & Simple guesses ain t so bad! What can we say about our symmetry? Gauss law in a baby universe discrete gauge symmetries stable against quantum gravity effects. But both -parity, and symmetries equivalent to Baryon and Lepton number conservation, are viable (anomaly-free). Again no clear preference for one or the other. What about Beyond-the-MSSM contributions? parity does not forbid proton decay! Anyway, all this was just to make the case... We certainly must consider all possibilities! RPV LHC, P. Skands p.16/36

27 Overview 1. Quick SUSY intro. 2. SUSY and the proton. 3. R Parity Violation with Trilinear Terms. (a) Lepton Number Violation (@ LHC). (b) Baryon Number Violation (@ LHC). 4. Lepton Number Violation with Bilinear Terms. (a) a SUSY origin of masses? (b) Measuring a angle at a hadron collider? RPV LHC, P. Skands p.17/36

28 $ % % # R conservation vs R violation. Conserves only allows sparticles to be produced in pairs and does not mediate LSP decay. Signature is missing (transverse) energy from escaping LSP s. At the LHC, squark and gluino pair production will dominate over most of parameter space. Typically, squarks and gluinos are among the heavier sparticles, hence other typical features are multiple jets and/or leptons which are split off in a chain of decays to lighter and lighter sparticles, ending with the (stable) LSP. Escaping LSP tricky mass reconstruction. RPV LHC, P. Skands p.18/36

29 % - Trilinear Lepton Number Violation LATER!. LLE ( LQD ) allows single slepton production at a linear collider (hadron collider). LQD also allows resonant squark/slepton collider. production at an Rich phenomenology. With just 2- and 3-body decays of sparticles to particles, more than 1200 new decay chanels! available from v ME s implemented into PYTHIA : LQD : LLE PS,Eur.Phys.J.C23:173(2002) RPV LHC, P. Skands p.19/36

30 Trilinear Lepton Number Violation LHC: 30fb SM: Missing E T TTBAR QCD HIGH P T QCD LOW P T ZZ/ZW/WW Z/W msugra P 9 : Missing E T LLE LQD MSSM QCD LOW : GeV GeV ; QCD HIGH : GeV N /Ntot per 10 GeV LLE LQD MSSM Missing E T Event distributions normalized to unit area for all msugra and LNV coupling points studied. RPV LHC, P. Skands p.20/36

31 % Trilinear Baryon Number Violation UDD, violates Baryon Number. Allows single (resonant) squark production from initial state. Allows 2-body decays of squarks to quarks and 3-body decays of gauginos to quarks. ME s for 2- and 3-body decays implemented from PYTHIA UDD : Sjöstrand+PS, Nucl.Phys.B659:243(2003) Unique colour structure, antisymmetric in fundamental rep indices new colour topologies not adressed by standard string fragmentation. RPV LHC, P. Skands p.21/36

32 BNV and String Topoloiges UDD term allows creation of 3 colour carriers, antisymmetric in colour, at large momentum separation. Ordinary string (e.g. ): Baryonic string (e.g. ): junction string topologies w/ junction(s). N p / N π χ decay. Junction protons. χ decay. Non-junction protons. qqbar w. E CM = m χ. qqbar w. E CM = 2/3 m χ p CM [GeV] RPV LHC, P. Skands p.22/36

33 Overview 1. Quick SUSY intro. 2. SUSY and the proton. 3. R Parity Violation with Trilinear Terms. (a) Lepton Number Violation (@ LHC). (b) Baryon Number Violation (@ LHC). 4. Lepton Number Violation with Bilinear Terms. (a) a SUSY origin of masses? (b) Measuring a angle at a hadron collider? RPV LHC, P. Skands p.23/36

34 Neutrino Summary Great surprise: I have done a terrible thing, I have invented a particle that cannot be detected W. Pauli Masatoshi Koshiba Raymond Davis Jr. Nobel prize 2002: Neutrinos have mass! RPV LHC, P. Skands p.24/36

35 + ' ' ( ' ' + Neutrino Summary Neutrino sector: a window to physics beyond SM? 1. Too few from atmosphere, can be explained by oscillations into : ev ) + 2. Too few into : from Sun, can be explained by oscillations ev ) 3. Bi-maximal mixing pattern: small. large, large, and + Explanations generally look like this: RPV LHC, P. Skands p.25/36

36 % ' ) Neutrino Masses : Dirac mass. Electroweak scale? : Majorana mass. High scale? ) % GeV No fun for high energy colliders... An alternative possibility could be with thus being rather small... of order, Testable at high energy colliders... RPV LHC, P. Skands p.26/36

37 Bilinear violation For us, the important consequences are: EW symmetry is broken by Higgs and sneutrino vev s, (i.e. ). Neutrinos mix with neutralinos mixing: In block form: RPV LHC, P. Skands p.27/36

38 $ % $ Bilinear Violation Determining the masses: #. Find diagonalizing matrix: to block-diagonal: First transform ; is projective, looks like: The matrix # RPV LHC, P. Skands p.28/36

39 $ $ $ # ' ' Bilinear Violation! So only 1 non-zero eigenvalue in # # ; 1 neutrino becomes massive at tree level. (Remaining neutrinos acquire mass at 1 loop).. ; RPV LHC, P. Skands p.29/36

40 ) Bilinear Violation Details depend on the particular SUSY scenario, but the general results are: The tree-level mass mass scale. generates the atmospheric The loop-induced corrections generate the Solar mass scale (i.e. mass pattern is hierarchical). With, the bi maximal mixing can be accomodated. RPV LHC, P. Skands p.30/36

41 Overview 1. Quick SUSY intro. 2. SUSY and the proton. 3. R Parity Violation with Trilinear Terms. (a) Lepton Number Violation (@ LHC). (b) Baryon Number Violation (@ LHC). 4. Lepton Number Violation with Bilinear Terms. (a) a SUSY origin of masses? (b) Measuring a angle at a hadron collider? RPV LHC, P. Skands p.31/36

42 Measuring a angle... BRPV couplings also responsible for LSP decay. Ratio of correlated with semileptonic branching ratios is strongly! RPV LHC, P. Skands p.32/36

43 Measuring a angle... model of SUSY origin of measuring at a hadron collider: mass can be checked by Note: this prediction is independent of the MSSM parameters. conserving To illustrate method, we have investigated a specific example, based on the SPS1a msugra point. (using SPHENO 2.2 together with PYTHIA 6.3, and SLHA interface to pass parameters) The Violating parameters are (in MeV): %! $ #! "! (chosen to fit neutrino data) RPV LHC, P. Skands p.33/36

44 %! & Measuring a angle... Total SUSY cross section for SPS1a:. Some shortcuts: Detector resolution and hadronization effects are ignored The detector : Calorimeter:. Inner detector:. Electrons (, GeV, ) Muons (, GeV, ) Taus (, GeV, $ "# ) Vertex resolution: 20 transverse and 0.5mm longitudinal. Triggers : 4j100, 2j100+e20/mu20, j100+2(e20/mu20). RPV LHC, P. Skands p.34/36

45 ! Measuring a angle... Events characterized by: Since Violating parameters are small, the only real deviation from MSSM phenomenology is LSP decay. pair production of squarks/gluinos dominate, with cascades down to LSP, which subsequently decays through LNV. Also due to smallness of LNV parameters, LSP is long lived. Decay length here is mm. very clean signature: 2 reconstructed detached vertices in fair fraction of signal events (define vertex reconstruction ellipsoid = 5 times resolution and reject tracks that intersect it). 100fb of data: reconstructed reconstructed & & decays. decays. $ "# precision on is couple of percent RPV LHC, P. Skands p.35/36

46 Summary & Conclusion parity: conserved or violated? Pros and cons on both sides. We just don t know. Possible sources of RPV: UDD, LLE, LQD, and Bilinear. UDD results in new types of colour topologies! augmentation of standard string fragmentation. Bilinear RPV also introduces new aspects: Sneutrinos play rôle of extra Higgses and acquire vevs. Neutrinos mix with Neutralinos. A low-scale seesaw mechanism results, whereby neutrinos become massive. Models consistent with neutrino data give predictions which can be tested at hadron colliders. RPV LHC, P. Skands p.36/36