1 / 29

THE STATUS OF THE BSM SCENARIOS

THE STATUS OF THE BSM SCENARIOS. (AFTER THE FIRST LHC PHASE). STEFAN POKORSKI, UNIVERSITY OF WARSAW. LHC 7-8 TeV. A GREAT TRIUMPH: 125 GeV HIGGS DISCOVERY. A PARTICLE APPARENTLY JUST AS THE ELEMENTARY HIGGS BOSON PREDICTED BY THE SM IS DISCOVERED!.

olympe
Download Presentation

THE STATUS OF THE BSM SCENARIOS

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. THE STATUS OF THE BSM SCENARIOS (AFTER THE FIRST LHC PHASE) STEFAN POKORSKI, UNIVERSITY OF WARSAW

  2. LHC 7-8 TeV A GREAT TRIUMPH: 125 GeV HIGGS DISCOVERY A PARTICLE APPARENTLY JUST AS THE ELEMENTARY HIGGS BOSON PREDICTED BY THE SM IS DISCOVERED! „APPARENTLY JUST” IS VERY IMPORTANT! TO APPRECIATE ALL THAT LET’S REMEMBER THE FOLLOWING….

  3. The Brout-Englert-Higgs mechanismin the gaugetheory of electroweakinteractionsneedsadditionalinteractions with spontaneouslybrokenGLOBAL symmetry e.gSU(2)xSU(2)SU(2) The BEH mechanism: Goldstonebosonsbecome the longitudinal modes of the gaugebosonsW, Zwhich acquiremasses.

  4. Simplestdynamicalsector (considered by many as a toy model) with global chiral symmetry (to be spontaneously broken) – self interacting scalar field, a doublet of SU(2)- IS NOW PROMOTED TOA REAL THING 3 Goldstonebosons + physicalelementaryscalar

  5. IN SM THE HIGGS COUPLINGS TO A PAIR OF FERMIONS OR GAUGE BOSONS ARE IN PROPORTION TO THEIR MASSES GIARDINO ET AL.’13 VERY UNLIKELY TO REPRODUCE IT BY ACCIDENT IT REALLY APPEARS AS THESM HIGGS PARTICLE! 3

  6. AT LEAST AT THE ELECTROWEAK SCALE, THE SM IS A CORRECT EFFECTIVE THEORY OF ELECTROWEAK INTERACTIONS IS THE SM A CONSISTENT THEORY UP TO THE PLANCK SCALE (LIKE e.g. QED)? YES! RENORMALISABLE NO LANDAU POLE UP TO Mp (ALMOST) STABLE VACUUM UP TO Mp THOSE CONCLUSIONS STRONGLY DEPEND ON

  7. THE HIGGS MASS HAPPENS TO BE WELL BELOW THE PERTURBATIVITY LIMIT AND AT THE EDGE OF THE VACUUM STABILITY BOUND (FOR THE TOP MASS AROUND 173 GeV) UP TO THE PLANCK SCALE

  8. IS THE SM A CONSISTENT THEORY UP TO THE PLANCK SCALE? YES BUT…. ISNT IT INDEED JUST AN EFFECTIVE THEORY, AN APPROXIMATION TO A DEEPER ONE (SIMILARLY AS QED, ALTHOUGH CONSITENT UP TO Mp, IS ONLY LOW ENERGY APPROXIMATION TO SM)? BY THE WAY, RENORMALISABILITY IS A GREAT VIRTUE OF EFFECTIVE THEORIES

  9. INDEED, IN SPITE OF NO HINT FOR NP AT THE LHC, DONT RUSH TO A TOO QUICK CONCLUSION ON THE VALIDITY OF THE SM TO PLANCK SCALE BECAUSE: HIGGS COUPLINGS VERSUS NEW SCALES: less than (3- 5) % deviations from the SM couplings VERY CHALLANGING: DEVIATIONS MAY BE OF THE ORDER OF THE PRESENT UNCERTAINITIES IN THE SM PREDICTIONS 8

  10. NO MATTER HOW CHALLANGING IT MAY BE TO SEE BSM PHYSICS THAT WAY, PRECISION HIGGS (AND TOP) PHYSICS LOOKS NOW LIKE A MUST! (CLIC, ILC, FCC?) 9

  11. WHY BSM, IN SPITE OF THE SUCCESS OF SM- CONT… EMPIRICAL EVIDENCE FOR BSM: DARK MATTER-- THIS IS NOW THE CRUCIAL PROBLEM IN PARTICLEPHYSICS (WITH A PARTICLE PHYSICS SOLUTION?) IF THERMAL EQUILIBRUM IN THE EARLY UNIVERSE IS THE SOURCE OF THE DM RELIC ABUNDANCE, THENTHE VALUE IS THE MAJOR HINT FOR A LOW SCALE NEW PHYSICS ! + DIRECT DETECTION + LHC -> RELEVANT PARAMETR SPACE BEGINS TO BE TESTED 11

  12. WHY BSM, IN SPITE OF THE SUCCESS OF SM- CONT… THE HIGGS PARTICLE WOULD BE THE FIRST EXAMPLE OF AN ELEMENTARY SCALAR PARTICLE! Sofar, Nature does not seem to likeelementaryscalars and the compositeonesarenever„unnaturally”light (much lighterthan the compositenessscale) unlesstheyare (pseudo) Nambu- Goldstonebosons, likepions in QCD NATURALNESS PROBLEM OF THE SM: ANY SHORT DISTANCE PHYSICS THAT COUPLES TO THE HIGGS (RH NEUTRINO, GUT PARTICLES..) WOULD INTRODUCE QUADRATIC SENSITIVITY OF VEV TO THOSE SCALES

  13. STRICTLY SPEAKING, IT IS NOT THE PROBLEM OF QUADRATIC DIVERGENCES IN THE SM: IF NO SCALES EXCEPT V=240 GEV AND IGNORING GRAVITY AS A PHYSICAL CUT-OFF, ONE MAY IGNORE THE PROBLEM (BECAUSE THE SM IS RENORMALISABLE)

  14. IN ADDITION, Higgs potential in the SM: describes but does not explain dynamically the origin of the Fermi scale IF IT HAS A DYNAMICAL EXPLANATION, THE SM SHOULD BE EMBEDDED IN A DEEPER THEORY! OTHERWISE, ANTHROPIC PRINCIPLE HAS TO BE INVOKED? BUT WE NEED ONLY ONE SCALAR. WHAT IF MORE ARE DISCOVERED?

  15. GIVEN THE APPARENT FINAL SUCCESS OF THE SM AND THE ABSENCE OF ANY EVIDENCE FOR NEW PARTICLES (SO FAR)— HAS THE CASE FOR BSM PHYSICS CLOSE TO THE ELECTROWEAK SCALE CHANGED? THE MOTIVATION REMAINS INTACT: DARK MATTER AND THE QUESTION ABOUT THE ORIGIN OF THE FERMI CONSTANT HOPEFULLY, THE SOLUTION TO THE DM IS PART OF A COMPLETE BSM THEORY CLOSE TO THE WEAK SCALE BUT IT IS ALSO CONCEIVEABLE THAT IT IS NOT THE CASE 10

  16. WITH THE ABOVE GUIDELINE, THERE ARE TWO MAIN DIRECTIONS: SUPERSYMMETRY COMPOSITE HIGGS MODELS (HIGGS DOUBLET AS A NAMBU- GOLDSTONE BOSON OF A NEW STRONG SECTOR WITH A SUFFICIENTLY BIG SPONTANEOUSLY BROKEN GLOBAL SYMMETRY E.G. SO(5)SO(4) BOTH CAN ACCOMMODATE 125 GeVMASS AND ALMOST SM-LIKE COUPLINGS 14

  17. SUPERSYMMETRY UNIQUE FEATURE: CANCELLATION OF QUADRATIC SENSITIVITY TO ARBITRARILY HIGH SCALES (FERMION – BOSON CANCELLATIONS) + ………. ……. ~ ………….. ………. 15

  18. FOR THE STOP MASS 1 TeV, SO WE GET 1% FINETUNING IN THE HIGGS POTENTIAL

  19. FERMION – FERMION CANCELLATIONS! EXP. SIGNATURES: HEAVY FERMIONS, SPIN 1 VECTOR MESONS 16

  20. COMPOSITE MODELS CAN ACCOMMODATE 125 GeV HIGGS BOSON BUT, IT’S A PHYSICAL PICTURE RATHER THAN A REAL MODEL A LOT OF ARBITRARINESS , NO EASY UV COMPLETION, ELECTROWEAK SECTOR LINKED TO NON-PERTURBATIVE PHYSICS ALL THAT CAN BE CONFRONTED WITH THE WELL KNOWN VIRTUES OF SUPERSYMMETRY 17

  21. MORE RECENTLY, REVIVAL OF THE IDEA OF CLASSICALLY SCALE INVARIANT SM (BARDEEN-1995) AT TREE LEVEL; EWSB BY QUANTUM CORRECTIONS-COLEMAN&WEINBERG ONLY LOGARITHMIC QUANTUM CORRECTIONS; IGNORING GRAVITY AS A PHYSICALCUT-OFF AND IN CONSEQUENCE IGNORING QUADRATIC DEPENDENCE ON Mp DIMENSIONAL TRANSMUTATION a LA QCD, EXCEPT THAT IN QCD THERE IS NO ELEMENTARY SCALAR…

  22. CAN ONE ALSO GET DM AND NEUTRINO MASSES IN SUCH ONE SCALE MODEL? TUNING IN MANY DIMENSIONLESS COUPLING? THEORETICALLY NOT WELL FOUNDED BUT INTRIGUING, IF A REALISTIC MODELS CAN BE CONSTRUCTED…

  23. TWO THEORIES THAT PREDICT THE HIGGS MASS IN A CERTAIN NARROW RANGE, AS A FUNCTION OF THE TOP MASS • SM EXTRAPOLATED TO THE PLANCK MASS • MINIMAL SUPERSYMMETRIC MODEL AS A FUNCTION OF THE TOP AND STOP MASS TAKE 1 TeV FOR STOPS TO KEEP THE HIGGS POTENTIAL REASONABLY „NATURAL”

  24. NON OBSERVATION OF THE SUPERPARTNERS IS CONSISTENT WITH THE HIGGS MASS BUT AT THE SAME TIME IS PUTTING THE IDEA OF NATURALNESSUNDER CERTAIN PRESSURE HOWEVER SUSY SEARCHERS ARE STILL QUITE FRAGMENTARY HIDDEN NATURALNESS? ( STEALTH SUPERSYMMETRY)

  25. Searches for top squarks • Dedicated searches for both direct and indirect production of top squarks; no signs of them (yet): • But still room left for naturalness: e.g. M(gluino)~1.5 TeV; m(stop)~300 GeV; m(LSP)~150 GeV • Really need more energy! CERN Accelerator School

  26. SUMMARY THE HIGGS DISCOVERY MAKES THE SM LOOKING AS A CONSISTENT THEORY UP TO VERY HIGH ENERGIES BUT THE CASE FOR THE BSM PHYSICS REMAINS INTACT: DARK MATTER AND DYNAMICAL ORIGIN OF THE FERMI CONSTANT. MAY OR MAY NOT BE UNDERSTOOD IN ONE THEORETICALFRAMEWORK? SUPERSYMMETRY REMAINS TO BE THE LEADING CANDIDATE CLASSICALLY SCALE INVARIANT SM (PLUS MINIMAL ADDITIONS)? THE EXPERIMENTAL EXPLORATION OF THE TeV SCALE IS STILL IN A VERY PRELIMINARY STAGE 25

  27. END

More Related