1 / 76

CTEQ 2003 Summer School Sant Feliu de Guixols 22-30 May 2003

CTEQ 2003 Summer School Sant Feliu de Guixols 22-30 May 2003. Enrico Tassi Univ. Autonoma de Madrid enrico.tassi@uam.es. An Experimental Introduction to Deep Inelastic Scattering. Overview (Lecture I) Early times

galeno
Download Presentation

CTEQ 2003 Summer School Sant Feliu de Guixols 22-30 May 2003

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. CTEQ 2003 Summer School Sant Feliu de Guixols 22-30 May 2003 Enrico Tassi Univ. Autonoma de Madrid enrico.tassi@uam.es An Experimental Introduction to Deep Inelastic Scattering • Overview (Lecture I) • Early times • - Nucleus/proton form factors • SLAC • - Early DIS results • Neutrino/muon fixed target exps • First QCD analyses • Towards HERA… Large Q2

  2. CTEQ 2003 Summer School Sant Feliu de Guixols 22-30 May 2003 Enrico Tassi Univ. Autonoma de Madrid enrico.tassi@uam.es An Experimental Introduction to Deep Inelastic Scattering For more on the HERA physics program see Claudia, Elke and Frank lectures • Overview (Lecture II) • HERA and ZEUS/H1 experiments • F2 determination • NC and CC high-Q2 cross sections • Results on F3 (both NC and CC) • H1 and ZEUS NLO QCD analyses (PDFs and αs) • Outlook on HERAII and beyond…

  3. This story is well known: H. Geiger and E. Marsden observed that α-particles were sometimes scattered through very large angles. Rutherford interpreted these results as due to the coulomb scattering of the α-particles with the atomic nucleus: Rutherford Scattering Rutherford taught us the most important lesson: use a scattering process to learn about the structure of matter θ ?

  4. Discovery of atomic nucleus → N. Bohr Old Quantum theory… Rutherford Scattering In a subsequent paper Geiger/Marsden precisely verified Rutherford theory

  5. The Franck and Hertz experiment I [mA] n=2 Electron scattering was then used extensively to investigate the atom’s electrons configurations 5 eV n=1 Hg

  6. Discovery of neutron (Chadwick 1932) Main information concerning geometric detailes of nuclear structure (mirror nuclei, fast neutron capture, binding energies etc) could be summed up in: R=r0xA1/3 fm with r0= 1.45 fm ρm= 0.08 nucl/fm3 and ρc=(Z/A)x0.08 (prot. charges)/fm3 Developments… • Quantum mechanics rapidly developed in the years 1924-27 • The nucleus composition remained a mistery (e.g. N714) till… α +Be → C + n Instrumental to the Fermi’s beta decay (n→peν) theory

  7. The nucleus form factor Stimulated by accelerators technology advances and fully muture QED various theoreticians (Rose (48), Elton(50)) started to calculate cross sections for elastic electron-Nucleus scattering Interference between the scattered wavelets arising from the different parts of the same,finite,nucleus Mott Nucleus form factor Phase-shift analysis

  8. The nucleus form factors

  9. e-p elastic scattering and proton’s factors Dirac and Pauli components of the proton’s Magnetic moment Proton as an extented object… Yennie,Levy,Ravenhall

  10. HEPL @ Standford: Klystron, Linac In the mid-’30 the Varian brothers (working as research assistants at the microwave department of the Standford University) developed the klystron exploiting a particular electromagnetic cavity (Rhumbatron) developed by W. Hansen This device played a fundamental role in the leading role that the Stanford HEPL was going to play in Linac devolpement… Russell and Sigurd Varian

  11. Organ pipe Linac basic unit The klystron Klystron

  12. Under the direction of E. Ginzton the HEPL started the construction of “small” scale linacs (MARKI,II,III). The half-completed MARKIII was instrumental to R. Hofstadter’s e-N e-p elastic scatterin experiments Assemblying Mark III… HEPL @ Standford: Klystron, Linac In the mid-’30 the Varian brothers (working as research assistants at the microwave department of the Standford University) developed the klystron exploiting a particular electromagnetic cavity (Rhumbatron) developed by W. Hansen This device played a fundamental role in the leading role that the Stanford HEPL was going to play in Linac devolpement… Russell and Sigurd Varian

  13. First evidence of elastic electron-Nucleus scattering D.W. Kerst (betatron)

  14. R. Hofstadter: e-N elastic scattering Fermi model C= (1.07±0.02)A1/3 fm t = (2.4±0.3) fm

  15. R. Hofstadter: e-p elastic scattering

  16. R. Hofstadter: e-d elastic scattering Electron deuteron scattering (Fermi motion…) First determinations of the proton’s form factors

  17. R. Hofstadter: e-N and e-p elastic scattering “As we have seen, the proton and neutron, which were once thought to be elementary particles are now seen to be highly complex bodies. It is almost certain that physicists will subsequentely investigate the constituent parts of the proton and neutron - the mesons of one sort or another. What will happen from that point on ? One can only guess at future problems and future progress, but my personal convinction is that the search for ever-smaller and ever-more-fundamental particles will go on as Man retain the curiosity he has always demonstrated” from the Nobel lecture, 1961

  18. One year later construction started While excavating for SLAC the workers discovered a nearly complete skeleton of a 10-foot mammal, Paleoparadoxia, which roamed earth 14 millions years ago… SLAC and the M-project • On april 10, 1956, Stanford staff met in Prof. W. Panofsky’s home to discuss • Hofstadter’s suggestion to build a linear accelerator that was at least 10 times • as powerful as the Mark III. This idea was called “The M(onster)-project” because • the accelerator would need to be 2 miles long!! • 1957 A detailed proposal was presented • 1959 Eisenhower said yes • 1961 The Congress approved the project ($114 Million dollars)

  19. SLAC : a success history

  20. The SLAC-MIT Experiment Under the leadership of Taylor, Friedman, Kendall

  21. Deep inelastic scattering and structure Fs Drell, Walecka, 62 Bjorken scaling

  22. First SLAC-MIT results Two unexpected results…

  23. Asymptotic freedom and QCD

  24. Other fixed target experiments (CCFR)

  25. Fixed targets results: An overview (PDG) F2: 1< Q2 < 200 GeV2 F3: 1< Q2 < 200 GeV2 FL See Wu-Ki and Alan lectures

  26. Towards HERA… What about the F2 behaviour at Low-x and High-Q2 ? ?? Buras (80)

  27. Towards HERA… See you on Saturday…

  28. CTEQ 2003 Summer School Sant Feliu de Guixols 22-30 May 2003 Enrico Tassi Univ. Autonoma de Madrid enrico.tassi@uam.es An Experimental Introduction to Deep Inelastic Scattering For more on the HERA physics program see Claudia, Elke and Frank lectures • Overview (Lecture II) • HERA and ZEUS/H1 experiments • F2 determination • NC and CC high-Q2 cross sections • Results on F3 and FL • H1 and ZEUS NLO QCD analyses (PDFs and αs) • Outlook on HERAII and beyond…

  29. Zeus H1 The HERA Collider The first and only ep collider in the world e± p 27.5 GeV 920 GeV Located in Hamburg √s = 318 GeV Equivalent to fixed target experiment with 50 TeV e±

  30. HERA I performance Mostly e+p collisions… HERA II upgrade:(goal: integrate 1fb-1/4years) - Severe background conditions - Huge effort by machine people/experiments - Restart expected in June

  31. Zeus Detector Complete 4π detector Tracking: - central tracking detector - Silicon μ-Vtx (operate in a B field of 1.43 T) Calorimeters: - uranium-scintillator (CAL) σ(E)/E=0.18/√E [emc] σ(E)/E=0.35/√E [had] - instrumented-iron (BAC) Muon chambers Both detectors asymmetric

  32. H1 Detector Complete 4π detector Tracking: - central jet chamber - z drift chambers - forward track. detector - Silicon μ-Vtx (operate in a B field of 1.2 T) Calorimeters: - Liquid Argon cal. - Lead-Fiber cal. (SPACAL) Muon chambers

  33. Kinematics

  34. Kinematics Reaching values of Q2 ≥ 3x104 GeV2 Kinematic limit defined by Q2=sxy sHERA=1.2x105 GeV2 Previous fixed-target experiments Reaching values of x < 10-6 Extension by several orders of magnitude in x and Q2

  35. NC and CC incl. processes NC: CC:

  36. where and with Inclusive cross sections and SFs Main observables of interest are the double differential cross sections: NC:

  37. Inclusive cross sections and SFs CC: Note: σSM = σBorn(1+δEW) …but full NLO in αs Reduced “cross sections”:

  38. Structure functions: QPM In the quark parton model (QPM) the NC SFs are: For the CC SFs:

  39. QCD evolution Evolution performed in terms of non-singlet, singlet and gluon densities: 2-loops splitting functions and αS :

  40. QCD Evolution QCD observables (SFs or reduced cross sections) are obtained Via a convolution of PDFs with Coefficients functions Eg: singlet NLO QCD electromagnetic structure function F2

  41. Towards HERA…

  42. F2 “ experimental evolution” time F2 rise towards low-x established with ~20 nb-1 Best F2 determination… so far ( 1996-97 data samples)

  43. Glue and Sea Main source of information on the gluon and sea densities of the proton

  44. F2 Analysis: Let’s take Zeus as an example Phase-space region: 6x10-5 < x < 0.65 2.7 < Q2 < 30000 GeV2 Very precise reconstruction of event’s characteristics and kinematic variables: Count nr. of events in appropriately defined (x,Q2) bins Extract reduced cross section Uncertainties are systematics dominated for Q2 < 800 GeV2

  45. At high-Q2 still statistics limited… → priority to the measurements at high-Q2 F2

  46. F2 scaling violations Reasonable agreement - between H1 and Zeus - With CTEQ and MRST

  47. High q2 NC Excellent description over seven order of magnitude Large unc. at high-Q2

  48. HERAI High-Q2 CC: (H1) The two data sets agree well with each other, tough the (99-00) data have a tendency to to be higher than the fit at highQ2 Large statistical uncertainties

  49. High-Q2 CC: (Zeus)

  50. EW Unification NC cross section sharply decreases with decreasing Q2 (dominant γexchange): ~ 1/Q4 CC cross section approaches a constant at low Q2 ~[M2W/(Q2+M2W)]2 Illustrate unification of the electromagnetic and weak interactions in Deep Inelastic Scattering Already a textbook figure…

More Related