16/08/06 CERN Students SessionsStefano Di Vita1 About mSUGO with Extra Vogon Dimensions in a Cubic Hyperspace in d=42 spontaneously broken by Boredons TexPoint fonts used in EMF: AAAAA A A A A A Stefano Di Vita Summer Students Sessions Talk

16/08/06 CERN Students SessionsStefano Di Vita2 Slide number Zero  Hello!  I’m Stèfano (not Stefàno, the accent goes on the ‘e’!!)  I’m a wanna-be theorist,  I’m a Summer student,  I’m studying SUperSYmmetry CERN And I’m having a great time! DO YOU EXPECT ME TO TALK ABOUT THAT? NO!

16/08/06 CERN Students SessionsStefano Di Vita3 Between the static quark model and QCD: basic facts about THE PARTON MODEL (A theorist hanging CERN) TexPoint fonts used in EMF: AAAAA A A STEFANO DI VITA (Universita’ degli Studi Roma Tre)

16/08/06 CERN Students SessionsStefano Di Vita4 Schedule  “Drive out” the quarks from their hadronic “nest”  Scare you all with some formulae  Spot some of the properties of partons  Prove that theoretical physics can be enormously boring… especially at 9.15 in the morning! That’s why I always wake up at 11!!

16/08/06 CERN Students SessionsStefano Di Vita5 DEEP INELASTIC SCATTERING (1) Kinematics 1960s SLAC-MIT experiments Note the elastic limit Q, v are INDEPENDENT!! Define the useful quantity

16/08/06 CERN Students SessionsStefano Di Vita6 DEEP INELASTIC SCATTERING (2) e-He analogy: spotting the CONSTITUENTS 1 x 0,20,4 Elastic e-He X=1 Elastic e-p X=0.25 INELASTIC e-He Around x=0.25 If inelastic scattering is due to INCOHERENT ELASTIC SCATTERING from the N=4 constituents (nucleons) Then the inelastic peak should be at After Hofstadter ( 1956)

16/08/06 CERN Students SessionsStefano Di Vita7 After Hofstadter ( 1956) DEEP INELASTIC SCATTERING (2) e-He analogy: POINTLIKE constituents 1 x 0,10,20,4 REDUCED Elastic e-p X=0.25 UNAFFECTED INELASTIC e- He Around x=0.25 REDUCED Elastic e-He X=1 Suppressed by a factor 6- 7 This behaviour is called SCALING and reveals the existence of POINTLIKE CONSTITUENTS of the target

16/08/06 CERN Students SessionsStefano Di Vita8 DEEP INELASTIC SCATTERING (4) electrons scattering on a proton Elastic peak Resonances Broad continuum (quasi- elastic constituent scattering) AT HIGHER Q 2 the cross section SCALES, indicating scattering from POINTLIKE CONSTITUENTS! Are they Gell-Mann’s quarks? After Bartel et al. ( 1968)

16/08/06 CERN Students SessionsStefano Di Vita9 Some UNAVOIDABLE Formulae: Structure Functions If the inelastic scattering is due to ELASTIC scattering from the constituents (mass m)

16/08/06 CERN Students SessionsStefano Di Vita10 Bjorken Scaling Hypothesis In the DIS regime fixed It MEANS that the photon scatters against something POINTLIKE: It’s GOOD because you can EXPERIMENTALLY TEST it!!! Summarizing, we can formulate the scaling hypothesis: IT WORKS!! After Miller et al.( 1972)After Friedman and Kendall ( 1972) Bjorken

16/08/06 CERN Students SessionsStefano Di Vita11 The Parton Model (1) LET PARTONS BE!! Pointlike particles Different kinds (different quarks?) Carry a fraction x of the proton momentum P Have a mass roughly a fraction x of the proton mass M The scaling variable R.P. Feynman

16/08/06 CERN Students SessionsStefano Di Vita12 The Parton Model (2): DIS at the parton level Hypotheses:  The proton is made up of POINTLIKE PARTONS  Inelastic scattering is a SUPERPOSITION of ELASTIC scattering e-parton Sum over parton types Parton charge Cross section “structure” for parton i Integral over momentum fractions Parton Density Function (Prob. of having a fraction x) Redefine the GLOBAL proton structure functions + “bonus” Callan-Gross relation

16/08/06 CERN Students SessionsStefano Di Vita13  pairs have OPPOSITE quantum numbers The Parton Model (3) implications: e.g. SEA QUARKS  PARTONS HAVE SPIN ½ (related to the Callan-Gross relation) THE QUARKS!! A proton (uud) remains a proton even if it contains an ARBITRARY NUMBER OF SEA QUARKS A PROTON Only the NET BALANCE matters!!

16/08/06 CERN Students SessionsStefano Di Vita14  I’m having CERN  DIS (ep>eX) evidences SCALING behaviour  Scaling is due to the existence of POINTLIKE CONSTITUENTS of p (partons)  Inelastic scattering is due to the INCOHERENT SUPERPOSITION of elastic scattering on partons  Parton model doesn’t forbid the presence of SEA QUARKS What did I tell you?

16/08/06 CERN Students SessionsStefano Di Vita15 The end… Thanks to  You all! I can’t believe you’ve been listening (?) to my delirium  The Summer Student Staff! You have arranged everything for us in such a brilliant way  My supervisors G. Altarelli and M. Seymour! I swear I’ll go back to my SUSY book after this talk  All my friends here! Thanx for the great time I’m having this summer… I owe you all another party : )  Myself! Thanx for reminding me I want to be a physicst

16/08/06 CERN Students SessionsStefano Di Vita16 What is missing? This is just the beginning. In fact:  I didn’t explain why quarks have SPIN ½  I didn’t mention neither neutrino-nucleon nor electron neutron DIS, so I couldn’t tell you that experiments support the hypotheses that  I didn’t tell you about the valence/sea quarks ratio  I didn’t tell you that there are VIOLATIONS to Bjorken scaling (see QCD!)  Quarks have FRACTIONARY charge  the existence of GLUONS