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Home , Grand Unified Theory

Vorlesung 10: Search for Beyond the (BSM)

• Standard Model : success and problems

• Grand Unified Theories (GUT)

• Supersymmetrie (SUSY)

– theory – direct searches

• other models / ideas for physics BSM

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 1 The Standard Model of ...

• fundamental : 3 pairs of plus 3 pairs of • fundamental : through gauge fields, manifested in – W±, Z0 and γ (electroweak: SU(2)xU(1)), – gluons (g) (strong: SU(3)) … successfully describes all experiments and observations! … however ...

the standard model is unsatisfactory:

• it has conceptual problems • it is incomplete ( ∃ indications for BSM physics)

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 2 Conceptual Problems of the Standard Model:

• too many free parameters (~18 masses, couplings, mixing angles) • no unification of elektroweak and strong –> GUT ; E~1016 GeV • quantum not included –> TOE ; E~1019 GeV • family replication (why are there 3 families of fundamental leptons?) • : need for precise cancellation of –> SUSY ; E~103 GeV radiation corrections • why only 1/3-fractional electric charges? –> GUT

indications for New Physics BSM:

• (n.b.: known from astrophysical and “gravitational” effects)

• Dark / / (n.b.: see above) • masses • matter / antimatter asymmetry

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 3 Grand Unified Theory (GUT):

• simplest symmetry which contains U(1), SU(2) und SU(3): SU(5) (Georgi, Glashow 1974) • multiplets of (known) leptons and quarks which can transform between each other by exchange of heavy “” bosons, und Y, with -1/3 und -4/3 charges, ± 0 as well as through W , Z und γ. d e+ X 0 + u u • direct consequence: decay p –> π e π0 u u } 4 M 30±1 ~ X ~10 yr 15 • proton lifetime: τp 2 5 for MX~10 GeV αGUT Mp 33 0 + experiment: τp > 8 x 10 yr (p –> π e ; Super-Kamiokande; 50 kT H2O) –> standard-SU(5)-GUT excluded! • is one of the generators of SU(5) group –> quantisation follows from exchange rules of charges!

–> ΣQi=0 for each multiplet (each family of quarks and leptons, e.g. [νe, e, 3(u, d)] ) –> explains exact 1/3-fractional quark charges by their 3 states of colour!

2 • further consequences of GUT: – small, but finite masses Mν ∼ Mµ / MX – existence of magnetic monopoles with mass ~1017 GeV 2 – sin θw(MX) = 3/8 Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 4

€ Grand Unified Theory (GUT):

• unification of “running” U(1), SU(2) und SU(3) coupling constants : α α α α α 2 1(MX) = 2(MX) = 3(MX) with: 1 = 8 em/3 = 8(e /4π)/3 ; α 2 θ 2 = g /4π; (g = e / sin w) α α 3 = s α(µ2 ) 11N − 4N α q2 = ; mit – β = c f • general energy dependence: ( ) 2 2 2 0 1− β0α(µ )ln( q /µ ) 12π

Nc= 0, 2, 3 for U(1), SU(2), SU(3),

Nf = 3 (number of generations of fermions)

• extrapolation of measured αi: • possible cure:

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 5

€ Supersymmetry

• generates cancellation of divergent radiation corrections –> solves Hierarchy Problem • postulates Symmetry between fermions and bosons: there is a new - (Boson-) partner for all known fundamental bosons (fermions)

Teilchen Spin S-Teilchen Spin ~ Quark Q 1/2 Squark Q 0 ~ l 1/2 Slepton l 0 γ 1 Photino γ~ 1/2 Gluon g 1 Gluino g~ 1/2 ~ W± 1 Wino W± 1/.2 ~ Z0 1 Zino Z0 1/2

• Higgs structure in minimal supersymmetric standard model (MSSM): 2 complex Higgs-doublets (8 free scalar parameters) –> 5 physical Higgs fields: ± 0 0 0 H , H1 , H2 , A . consistency requirement: M 0 ≤130 GeV H1 • gauginos ( γ ˜ , W ˜ ± , Z˜ ) mix with higgsinos and form as eigenstates: ± 0 4 charginos ( χ 1 ,2 ) und 4 neutralions ( χ 1 ,2,3,4 )

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 6

€ € € € Supersymmetry

• 124 free parameters (!!) to describe masses and couplings of SUSY particles; β β 2 2 2 thereof, angle , with tan( ) = v1/v2 . only known condition: (v1 + v2 ) = 246 GeV • new conserved quantity: “R-parity”: R = (-1)3(B-L)+2S (B, L: -/; S: Spin); R = +1 for normal matter, R = –1 for supersymmetric particles (*)

• if R-parity conserved : - Susy particles are produced pair wise (associated) - Susy particles all decay into “lightest Susy Particle”, LSP, which itself is stable. –> Dark Matter - cosmological arguments: LSP is charge-neutral und does not carry –> only ! –> leads to signature of missing energy (like neutrinos). • Supersymmetry with masses of O(1 - 10 TeV) change energy dependence of coupling constants, so that “unification” happens at E ~ 1016 GeV (see figure on page 5) –> proton lifetime increases to >> 1032 years within SUSY-GUT. n.b.: since ~ 2001 there is an alternative Ansatz to generate cancellation of quantum corrections also through particles with equal spin: „ models“. (*) note that R-parity is a multiplicative quantity - similar to Parity or CP, unlike additive quantities as e.g. charge Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 7 the birth of SUSY… >2500 citations

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 16 8 Prof. Dr. Julius Wess MPP and LMU + 2007 Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 9 Specific SUSY Models

MSSM: minimal supersymmetric standard model; minimal particle content; R-parity conservation; symmetry broken ‘by hand’ (adding to L all ‘soft’ terms consistent with SU(3) x SU(2) x U(1) gauge invariance)

SUGRA: ; spontaneous symmetry breaking (SB) in ‘hidden sector’; gravity is messenger of SB to MSSM sector; irrelevant for physics in TeV region € mSUGRA: minimal Supergravity; all squarks and sleptons have common mass at GUT scale: m q˜ (M GUT ) = m ˜ (M GUT ) = m 0 l and all gauginos have same mass m1/2 at GUT scale

GMSB: gauge mediated SUSY €breaking; gravitino is (usually) the LSP; phenomenology depends on NLSP

R-parity violating: violate either lepton- or baryon number conservation

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 10 Example of SUSY mass spectrum:

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 11 Supersymmetry: direct searches

exp. signatures : backgrounds: • several high energy leptons, plus ← W, Z , b, c decays • several high energy hadronic jets, plus ← QCD • missing (transverse) energy / momentum (χ0) ← ν from b, c decays

exp. signatures if R-parity not conserved: • end points of mass spectra ← combinatorics • mass differences of decay products in decay chains ← combinatorics

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 12 SUSY: Production at Hadron (LHC)

• production dominated by color-charged particles • cross sections determined by squark/gluino masses

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 13 SUSY: exp. searches and uncertainties

search for: signatures of multi-lepton, multi-jets, missing energy

theoretical uncertainties: • cross sections • contributions of higher orders of perturbation theory • initial and final state radiation effects • underlying event (proton remnants)

experimental uncertainties: • jet reconstruction (E-calibration, resolution) • pile-up at high luminosities • reconstruction and resolution of missing energy • lepton identification –> should possibly be calibrated with data (not MC!)!

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM SUSY: background

• real ETmiss e.g. from W/Z + Jets, tt + Jets (neutrinos)

• „fake“ ETmiss from detector effects and QCD events

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 15 SUSY: experimental background

through: • accelerator • beam-gas events • „hot“ calorimeter cells • and many others Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 16 Example 1: search for squarks and gluinos

using final states with high pT jets and large ET (and NO leptons)

miss Meff = ET + Σ |pTjet|

arXiv:1109.6572v1 [hep-ex] Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 17 Example 1: search for squarks and gluinos (strong production) using final states with high pT jets and large ET (and NO leptons)

exclusion of gluino masses up to 1900 GeV exclusion of squark masses up to 1000 GeV Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 18 Example 2: search for neutralino-chargino production (weak production)

using final states with high pT leptons and large ET

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 19 Results of main SUSY searches

SUSY: mass limits in the range 0.5-2 TeV (within constrained models)

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 20 Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 21 verifying SUSY:

• if indications or evidence for SUSY found, one should –> find the super partners of all SM particles –> verify that their spins are different by 1/2 –> verify quantum numbers and couplings –> verify correct predictions of masses

• excess of events - also compatible with other (exotic) models? –> , ....

• needs: (precision-) measurements of –> masses –> production cross sections –> branching ratios –> decay angular distributions .... Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 22 other en vogue models of BSM:

• composite models (excited quarks & leptons)

• new symmetries (new heavy gauge bosons) • (micro black holes,…) • models (new gauge interactions) • (GUT) • …

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 23 ADD model of large extra dimensions:

• fields of SM are confined to 3+1- dimensional membrane

• gravity propagates to n additional spatial extra dimensions

• extra dimensions are compactified on an n-dimensional torus / sphere of radius R

n+2 2 -n • Planck-mass in 4+n dimensions : MD ~ MPl R may approach TeV scale for large n → micro black holes?

1 N. Arkani-Hamed, S. Dimopoulos, G. Dvali (1998). "The Hierarchy problem and new dimensions at a millimeter". Physics Letters B429 (3–4): 263–272. arXiv:hep-ph/9803315. 2 N. Arkani-Hamed, S. Dimopoulos, G. Dvali (1999). "Phenomenology, astrophysics and cosmology of theories with submillimeter dimensions and TeV scale ". D59 (8): 086004. arXiv:hep-ph/9807344. Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 24 exp. signatures of exotic BSM models:

• high-mass resonances decaying into jets, leptons, bosons

• high system involving visible and invisible objects

• specific event properties (angular distributions,…)

signal signal

signal background background background

pair mass energy of system internal property (jets, leptons, bosons) (visible, invisible) (e.g. angular distribution)

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 25 exp. signatures of exotic BSM models:

• high-mass resonances decaying into jets, leptons, bosons

• high system energies involving visible and invisible objects

• specific event properties (angular distributions,…)

extensive searches have not shown any significant deviations from SM and thus, no compelling signature of any physics BSM

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 26 Searches for composite / excited quarks 13 TeV data: Dijet Resonant Searches

ATLAS-CONF-2016-069

excludes e.g. excited quarks with masses < 5.6 TeV, and quantum BHs with masses < 8.7 TeV (n=6)

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 27 summary of (model dependent) exclusion limits:

so far: no positive signals ➔ mass range exclusions Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 28 “Absence of evidence is not evidence of absence”

meaning:

no sign of physics BSM from Run-I / Run-II data, but unexplored phase space still large!

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 29 ATLAS monojet event (pt=1.7 TeV) with large missing Et (1.7 TeV)

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 30 Summary :

• so far, SM still describes data (LHC at 7, 8 and 13 TeV) miss • exp. signatures for BSM: multi-jets , multi-leptons , ET • direct searches for BSM physics: no significant signals yet • so far: e.g. exclusion of squarks, gluinos w. masses < O(1 - 2 TeV)

• large part of phase space still open for physics beyond SM • SUSY is (still) main candidate for BSM • large phase space due to many free parameters • „standard” SUSY models: MSSM, (m)SUGRA, CSSM...

• LHC still has large discovery potential for BSM (14 TeV; hL) • “guaranteed” discovery for SUSY masses of several TeV • specifying SUSY/BSM model (if found) will be difficult at LHC => he-LHC; FCC Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 31 Literature:

• Supersymmetry in Physics. Michael E. Peskin, SLAC-PUB-13079, 72pp. e-Print: arXiv:0801.1928 [hep-ph]

• Supersymmetry and cosmology. Jonathan L. Feng, 66 pp., e-Print: hep-ph/0405215

• A Supersymmetry primer. Stephen P. Martin (Michigan U.) . Sep 1997. 88pp. e-Print: hep-ph/9709356

• Supersymmetry and supergravity. J. Wess (Munich U.) , J. Bagger (Johns Hopkins U.) . 1992. 259pp. Princeton, USA: Univ. Pr. (1992) 259 p.

• SUSY Searches with the ATLAS Experiment. Pawel Klimek, http://inspirehep.net/record/ 1473526/files/v47p1505.pdf.

• SUSY searches with the CMS Detector. F. Giordano, http://inspirehep.net/record/1485944/ files/fulltext.pdf.

next lecture (15.1.18): Higgs (1)

Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 32