The EMC Effect Still Puzzles After 30 Years

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CERN Courier May 2013 EMC effect Modulators, Power Supplies, RF Transmitters IPAC 2013 May 12 - 17 • Shanghai, China Visit us in Booth 11 The EMC effect still puzzles after 30 years

™ PowerMod Thirty years ago, high-energy muons at Solid-State Pulsed Power Systems CERN revealed the ﬁ rst hints of an effect • Compact, Rugged, Reliable that puzzles experimentalists and theorists • Voltages to 500 kV alike to this day. Complete Turnkey Systems • Currents to 5 kA • Frequencies to Hundreds of kHz Contrary to the stereotype, advances in science are not typically • Hundreds of Installations Worldwide about shouting “Eureka!”. Instead, they are about results that make a researcher say, “That’s strange”. This is what happened 30 years ago when the European Muon collaboration (EMC) at CERN 35 Wiggins Avenue • Bedford, MA 01730 USA • www.divtecs.com looked at the ratio of their data on per-nucleon deep-inelastic muon scattering off iron and compared it with that of the much smaller nucleus of deuterium. The data were plotted as a function of Bjorken-x, which in deep- inelastic scattering is interpreted as the fraction of the nucleon’s momentum carried by the struck quark. The binding energies of nucleons in the nucleus are several orders of magnitude smaller Fig. 1. A plot of the EMC data as it appeared in the November than the momentum transfers of deep-inelastic scattering, so, 1982 issue of CERN Courier. This image nearly derailed the naively, such a ratio should be unity except for small corrections highly cited refereed publication (Aubert et al. 1983) because for the Fermi motion of nucleons in the nucleus. What the EMC the editor argued that the data had already been published. experiment discovered was an unexpected downwards slope to the ratio (fi gure 1) – as revealed inCERN Courier in November 1982 and then published in a refereed journal the following March (Aubert et al. 1983). shadowing This surprising result was confi rmed by many groups, culmi- 1.0 Pearson Electronics designs and manufactures nating with the high-precision electron- and muon-scattering data D custom Current Monitors for use in the beam from SLAC (Gomez et al. 1994), Fermilab (Adams et al. 1995) 2 tube, and large aperture clamp-on Current

and the New Muon collaboration (NMC) at CERN (Amaudruz Ca /F 2

Monitors applied outside the beam tube. F et al. 1995 and Arneodo et al. 1996). Figure 2 shows representative Pearson Monitors measure sub-milliamp data. The conclusions from the combined experimental evidence 0.8 EMC effect currents. Pulse rise times as fast as 1.5 were that: the effect had a universal shape; was independent of the nanoseconds can be viewed accurately. Many squared four-momentum transfer, Q2; increased with nuclear mass clamp-on and fixed aperture models are in number A; and scaled with the average nuclear density. stock and available for immediate delivery. 0.01 0.1 1 x A simple picture The primary theoretical interpretation of the EMC effect – the Fig. 2. The ratio of the deep-inelastic cross-sections of calcium region x > 0.3 – was simple: quarks in nuclei move throughout (Ca) to that of deuterium (D) from NMC (solid circles) and SLAC a larger confi nement volume and, as the uncertainty principle (open circles). The downward slope from 0.3 < x < 0.7 and implies, they carry less momentum than quarks in free nucle- subsequent rise from x > 0.7 is a universal characteristic of EMC ons. The reduction of the ratio at lower x, named the shadow- data and has became known as the EMC effect. The reduction of ing region, was attributed either to the hadronic structure of the ratio at lower values of x, where valence quarks should no ▲ the photon or, equivalently, to the overlap in the longitudinal longer play a signifi cant role, is known as the shadowing region.

CERNCOURIER www. V o l u m e 5 3 N u m b e r 4 M a y 2 0 1 3 CERN Courier May 2013 SETTING SCIENCE EMC effect IN MOTION 0.5 5.0 197Au Whether it is attaining sub-nanometre positioning or controlling SRC plateau 0.4 hundreds of precision axes of movement in a synchrotron ring, 4.0 56Fe Delta Tau sets the global benchmarks for accuracy and control. 12C D Motion controllers 3.0 0.3 / ␴

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• Three current ranges - 250mA continuous/750mA peak, 1A cont/3A peak, 5A cont./15A peak EMC effect –dR • Voltage operating range 12V – 60V DC 1.0 • Epics and Tango compliant 3He • Software programmable to run any mix of stepper, DC brushed or AC servo motor 0.1 • Fibre optic link to higher power external MACRO amplifiers 0.4 0.7 1.0 1.3 1.6 1.9 Power supplies x d • Two power versions available 1600VA and 500VA 0 • Compact 1U form factor Fig. 3. While fi gure 2 focuses on lower values of x, this focuses on • Each supply can be connected to up to 4 controllers • Individually thermally protected outputs the valence-quark region. In this region, the slope of the EMC • Separate power sources for motors, axis flags and control voltages effect in the region 0.3 < x < 0.7 and the x > 1 plateaux from –0.1 • Integral regeneration circuit with thermal overload protection nucleon–nucleon short-range correlation (SRC) can be clearly 0 1 2 3 4 5 6

seen. Both the EMC effect and the plateaux are more or less a2(A/d) Delta Tau (UK) Limited independent of Q2, while the dip at x = 1 fi lls in as Q2 increases. Unit 2 Faraday Close, Gorse Lane Industrial Estate, Clacton on Sea, Essex CO15 4TR Fig. 4. The slope of the EMC effect, dR/dx for 0.3 < x < 0.7 with A D Telephone: +44 (0)1255 221055 Fax: +44 (0)1255 225 391 Email: [email protected] direction of small-x partons from different nuclei. These notions R = F2 /F2, versus the magnitude of the observed x > 1 plateaux, www.deltatau.co.uk gave rise to a host of models: bound nucleons are larger than denoted as a2, for various nuclei. For data that were taken by free ones; quarks in nuclei move in quark bags with 6, 9 and completely different groups, the linearity is striking and has even up to 3A quarks, where A is the total number of nucleons. caused renewed interest in understanding the cause of both More conventional explanations, such as the inﬂ uence of nuclear effects. The inset drawings illustrate the kinematic difference of binding, enhancement of pion-cloud effects and a nuclear pionic deep-inelastic EMC-effect scattering and the scattering from a fi eld, were successful in reproducing some of the nuclear deep- correlated pair in x > 1 kinematics. inelastic scattering data. No Liquid Nitrogen Solid State Design It was even possible to combine different models to produce new suggested that the effect follows local nuclear density. In other Easy to Use Low Cost ones; this led to a plethora of models that reproduced the data (Gee- words, even in deep-inelastic kinematics, 9Be seemed to act like saman et al. 1995), causing one of the authors of this article to write two alpha particles with a single nearly free neutron, rather than that “EMC means Everyone’s Model is Cool”. It is interesting to note like a collection of nucleons whose properties were all modifi ed.

SUPER SDD that none of the earliest models were that concerned with the role of This led experimentalists to ask if the x > 1 scaling plateaux 5.9 two-nucleon correlations, except in relation to six-quark bags. (CERN Courier November 2005 p37) that have been attributed to keV The initial excitement was tempered as deep-inelastic scattering short-range nucleon–nucleon correlations – a phenomenon that is 55Fe became better understood and the data became more precise. Some also associated with high local densities (CERN Courier January/ of the more extreme models were ruled out by their failure to match February 2009 p22) – could be related to the EMC effect. Figure 3 eV FWHM well known nuclear phenomenology. Moreover, inconsistency with shows the kinematic range of the EMC effect together with the x > 1

Counts 125 25 mm2 x 500 µm the baryon-momentum sum rules led to the downfall of many other short-range correlation (SRC) region. While the dip at x = 1 has been 2 11.2 µs peaking time models. Because some of them predicted an enhanced nuclear sea, shown to vary rapidly with Q , the EMC effect and the magnitude of P/B Ratio: 8200/1 the nuclear Drell-Yan process was suggested as a way to disentan- the x > 1 plateaux are basically constant within the Q2 range of the gle the various possible models. In this process, a quark from a pro- experimental data. Plotting the slope of the EMC effect, 0.3 < x < 0.7, Energy (keV) ton projectile annihilates with a nuclear antiquark to form a virtual against the magnitude of scal- photon, which in turn becomes a leptonic pair (Bickerstaff et al. ing x > 1 plateaux for all of the 1984). The experiment was done and none of the existing models A signifi cant shift available data, as shown in XR-100SDD X-Ray Detector and provided an accurate description of both sets of data – a challenge figure 4, revealed a striking X-123SDD Complete X-Ray Spectrometer with X-ray that remains to this day (Alde et al. 1984). in experimental correlation (Weinstein et al. detector and preampliﬁ er, digital pulse processor, understanding 2011). This phenomenological MCA, and power supply New data occurred when relationship has led to renewed A signifi cant shift in the experimental understanding of the EMC 9 interest in understanding how 9 new data on Be AMPTEK Inc. effect occurred when new data on Be became available (Seely strongly correlated nucleons in et al. 2009). These data changed the experimental conclusion that the nucleus may be affecting the E-mail: [email protected] became available ▲ www.amptek.com Please see web site for vacuum applications the EMC effect follows the average nuclear density and instead deep-inelastic results. 37

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CERNCOURIER www. V o l u m e 5 3 N u m b e r 4 M a y 2 0 1 3 CERN Courier May 2013 Anniversary

In February 2013, on nearly the 30th anniversary of the EMC Magnets publication, experimentalists and theorists came together at a special workshop at the University of Washington Institute of Nuclear Theory to review understanding of the EMC effect, discuss recent advances and plan new experimental and theoretical efforts. In N E W 6 C H A N N E L and coils particular, an entire series of EMC and SRC experiments are planned HIGH VOLTAGE NIM-MODULE for the new 12 GeV electron beam at Jefferson Lab and analysis is www.scanditronix-magnet.se underway of new Drell-Yan experimental data from Fermilab. ・ 6 channel (independent) A new life Although the EMC effect is now 30 years old, the recent experi- ・ full front panel control mental results have given new life to this old puzzle; no longer is Every Model Cool. Understanding the EMC effect implies under- ・ 1.44“ TFT display standing how partons behave in the nuclear medium. It thus has far-reaching consequences for not only the extraction of neutron ・ USB / CAN interface information from nuclear targets but also for understanding effects such as the NuTeV anomaly (CERN Courier September 2009 p9) or ・ ripple and noise max. 5mV the excesses in the neutrino cross-sections observed by the Mini- BooNe experiment (CERN Courier May 2007 p8). ・ 1/12 NIM standard cassette

● Further reading For more about the workshop at the University of Washington Institute of Nuclear Theory, see www.int.washington.edu/ PROGRAMS/13-52w/. www.iseg-hv.com/nhs A Adams et al. 1995 Z. Phys. C 67 403. CERN Courier - BOP GL 2013_Layout 2 4/5/13 12:03 PM Page 1 D Alde et al. 1990 Phys. Rev. Lett. 64 2479. +49.351.26996-0 | www.iseg-hv.com P Amaudruz et al. 1995 Nucl. Phys. B441 3. M Arneodo et al. 1996 Nucl. Phys. B481 3. A NEWGENERATION of BIPOLARPOWER J J Aubert et al. 1983 Phys. Lett. B 123 275. R Bickerstaff et al. 1984 Phys. Rev. Lett. 53 2532. BOP1KILOWATTfrom KEPCO D F Geesaman et al. 1995 Ann. Rev. Nucl. Part. Phys. 45 337. UHV Feedthroughs Muons, Inc. http://www.muonsinc.com/ Model BOP J Gomez et al. 1994 Phys.Rev. D 49 4348. 20-50GL J Seely et al. 2009 Phys. Rev. Lett. 103 202301. Particle beam and accelerator research, L Weinstein et al. 2011 Phys. Rev. Lett. 106 052301. development, design, and realization using advanced technologies: Résumé 1) Sources and Beams: p, µ, e, γ, Η−, L’effet EMC, encore une énigme 30 ans après polarized ions

Il y a trente ans, les membres de la collaboration EMC 2) RF: NC fast-tunable, dielectric-loaded, BUILT-IN ARBITRARY WAVEFORM GENERATOR (Collaboration européenne du muon) au CERN découvraient and SRF cavities, magnetrons, couplers, HOM dampers BOP 1KW BOP-GL Series un effet inattendu en rapportant leurs mesures de la diffusion • True 4-quadrant programmable voltage and • Standard modification profondément inélastique du muon au nombre de nucléons : 3) Magnets: HTS High-Field, Helical current power supplies of the 1KW les fonctions de structure étaient différentes s’agissant du fer Beam Cooling • Capable of full source and sink operation • Optimized for exceptionally et s’agissant du deutérium, qui est un noyau beaucoup plus • Achieve low dissipation and high efficiency, low current ripple and noise 4) Simulations: G4beamline, ACE3P, when sinking power from a load • Improved stability léger. En représentant le rapport fer/deutérium en fonction de la many codes • Recuperate the energy for re-use. (drift and temperature) fraction de l’impulsion du nucléon portée par le quark frappé, 5) Detectors: profile monitors, fast TOF Bi-directional power factor correction (PFC) • Ideal for driving inductive les expérimentateurs ont découvert une pente descendante circuit allows transparent energy interchange loads such as large magnets inattendue. Ce résultat surprenant a été confi rmé par de nombreux 6) Applications: Colliders, Factories, without dissipative sinking or motors ADS Reactors, SNM detection, SMES, • Keypad controls for automatic creation and groupes, mais il reste une énigme. Des données récentes sur le • Pass smoothly through zero 9 IPT-Albrecht GmbH monoenergetic photons, rare decay display of waveforms and complex patterns Be ont relancé l’intérêt pour cette question, en montrant que des without switching providing Waldweg 37 experiments, 6D muon beam cooling, • Meet EN61000-3-2 harmonic limits true ± voltage and ± current corrélations nucléon-nucléon à courte distance pouvaient être liées 77963 Schwanau / Germany and anything needing creative solutions • Built-in EN55022 Class B input EMI filter provided à l’effet EMC. Tel +49 - 7824 / 66 36 33 For more information visit: Seeking partnerships for , Jefferson Lab, , University of Fax +49 - 7824 / 66 36 66 www.kepcopower.com/bophi.htm Douglas Higinbotham Gerald A Miller commercial ventures Washington, Or Hen, Tel Aviv University, and Klaus Rith, University of Email: [email protected] KEPCO, INC. • 131-38 Sanford Ave. • Flushing, NY 11355 USA • Tel: (718) 461-7000 www.ipt-albrecht.de Fax: (718) 767-1102 • Email: [email protected] • www.kepcopower.com Erlangen-Nürnberg. Please visit us at Booth 34 at IPAC13

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CCMay13Ad_Muons.indd 1 08/04/2013 14:31 CERNCOURIER www. V o l u m e 5 3 N u m b e r 4 M a y 2 0 1 3 Document1 8/8/06 10:44 Page 1

CERN Courier May 2013 Faces & Places

a W a r D s Engineering prize honours internet and Web pioneers

Five engineers whose work, beginning in the 1970s, led to the internet and the World Wide Web have together won the inaugural Queen Elizabeth Prize for Engineering. Robert Kahn, Vinton Cerf, Louis Pouzin, Tim Berners-Lee and Marc Andreessen were announced on 18 March as the winners at the Royal Academy of Engineering in London. Kahn, Cerf and Pouzin receive the award for their contributions to the protocols that make up the fundamental architecture of the internet. French computer scientist Pouzin invented the datagram and designed an early packet communications network known as CYCLADES in the early 1970s. His work was broadly used by Americans Kahn and Cerf in the development of TCP/ IP. Berners-Lee created the World Wide Web at CERN in 1989 and American Marc Andreessen wrote the Mosaic browser that is credited with popularizing the Web. By sharing their work freely and without restriction these pioneers allowed the Tim Berners-Lee is reunited with the historic NeXT computer at CERN during celebrations Visit us at internet and the Web to be adopted rapidly for the 20th anniversary of the web in 2009 (CERN Courier May 2009 p24). He used this around the world and to grow organically computer to develop and run the fi rst Web server, multimedia browser and Web editor. Booth 605 thanks to open and universal standards. Measuring magnetic Additionally, they have served as technical 330 petabytes of data a year – enough to for a ground-breaking innovation in and political stewards of the internet and the transfer every character ever written in every engineering that have benefi ted humanity. New Photomultiplier HV Base field transients? web over the past 30 years as it has grown book ever published 20 times over. It is administered by the Royal Academy of Using photomultipliers is now even easier with a new from its experimental phase to hosting The Queen Elizabeth Prize for Engineering. range of compact, low noise, HV Bases from The Fast Digital Integrator FDI2056 is the world’s 50 billion pages of information today. Today Engineering is a £1 million global The winners are due to come to London in ET Enterprises. fastest and most sensitive voltage integrator. a third of the world’s population uses the engineering prize designed to reward June for the formal presentation of the prize at

Incorporating socket, voltage divider and HV - Photo: Scott Maxwell www.agence-arca.com internet and it is estimated to carry around and celebrate the individuals responsible Buckingham Palace by Queen Elizabeth II. supply, they are suitable for use with a wide range of photomultipliers operating in analogue, For the first time it is possible to measure fast, low-level pulse counting or photon counting modes. magnetic field disturbances such as eddy currents in a switched magnet. . range of input voltage (5V to 15V) . output voltage adjustable from 100V to 2000V A complete and upgradable . very low power solution for your most exacting . high stability magnetic measurements. Visit our new website for further information.

ET Enterprises is now your single source for ‘Electron Tubes’ and ADIT photomultipliers, including many Photonis replacements. Now it’s possible! Designed at the CERN Use our new interactive website to search our complete range of products or follow the contact links to discuss your application. Recipients of the Fundamental Physics project and the CMS and ATLAS Hawking also received a special prize, while ET Enterprises Limited, Riverside Way, Uxbridge, UB8 2YF, UK Prize Foundation’s special prize in experiments from the time that the LHC was quantum-fi eld theorist Alexander Polyakov Phone: +44 (0)1895 200880 fundamental physics, announced in approved by the CERN Council in 1994. received the 2013 Fundamental Physics Fax: +44 (0)1895 270873 [email protected] December (CERN Courier January/ Here Guido Tonelli shares the stage with Prize for his work in fi eld theory and string www.et-enterprises.com February 2013 p36), accepted their awards (left to right): Lyn Evans, Michel Della theory. The event was hosted by the actor ADIT Electron Tubes, 300 Crane Street, at a ceremony in Geneva on 20 March. The Negra, Tejinder Virdee, Peter Jenni, Joe Morgan Freeman, who took the opportunity Sweetwater, Texas 79556, USA Phone: (325) 235 1418 Pantone 286 Pantone 032 prize was shared by leaders of the LHC Incandela and Fabiola Gianotti. Stephen to visit CERN and the LHC tunnel (right). Fax: (325) 235 2872 [email protected] www.electrontubes.com catch the light www.metrolab.com Magnetic precision has a name 41

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