With the advent of microproces­ off-line processing effort to elimi­ under way in the Data Handling sors, a solution to this problem could nate bad triggers. Division. Two of these are pro­ be in sight. Micros could be incorpo­ As well as being used in the data grammable emulators (one being rated into experimental set-ups to collection system, micros would also based on the IBM 370/168 and the carry out a second level of data be useful for control and monitoring other on the Digital Equipment PDP- selection after the initial hard-wired functions, where their use is already 11 ), while the third is a very fast triggering — an example of the so- common wherever routine process microprogrammable unit called called 'distributed processing' ap­ control is important. The use of off- ESOP. proach where computing power is the-shelf microcomputers in accel­ High energy physics has still a lot laced as far upstream as possible in erator control systems, for example, to learn about microprocessor appli­ tne data handling process. In this is already relatively widespread. cations, and there is some way to go way the demand on the downstream Some limited applications outside before their feasibility is demon­ central computer would be reduced, the control area are already being strated and practical problems, such and the richness of the data sample made in experiments, a notable as programming, are overcome. increased. example being the CERN/Copen- However this year could see some The micros would filter the read­ hagen / Lund / Rutherford experi­ of these initial projects come to frui­ out in the few microseconds before ment now being assembled at the tion, and the early 1980s could live the data is transferred to the experi­ CERN Intersecting Storage Rings up to Zanella's expectations as the mental data collection system. (see April issue, page 65). time when the microprocessor be­ Zanella is convinced that this could Microcomputer projects are now comes a routine part of the high significantly improve the quality of being tackled at several Laborato­ energy physicists' toolkit. the data and reduce the subsequent ries. At CERN three projects are

Around the Laboratories

vour. Unlike charged current interac­ target slab of thickness 8 cm. CERN tions, the outgoing lepton cannot be Between these modules are 12 cm First CHARM results detected, and additional information gaps filled with 20 scintillation is required to fix momentum trans­ counters and 3 cm square drift fer. tubes. Each target plate is sur­ The second experiment lined up in While in charged current inter­ rounded by a magnetized iron frame, the CERN beam (after the actions it is sufficient to measure just and the whole assembly is backed by CERN / Dortmund / Heidelberg / the energy of the produced a magnetized iron calorimeter. Saclay detector) is the 'CHARM' shower, studies also This arrangement enables the experiment — the handy acronym require the direction of the hadron experimenters to follow the flow of coming from the CERN/Hamburg/ shower to be determined. hadronic energy, and in effect com­ Amsterdam / Rome / Moscow The CHARM detector thus com­ bines traditional calorimeter and collaboration with blatant disregard bines the features of traditional visual detection techniques. As neu­ for alphabetical order. hadron calorimeter with a fine­ tral hadronic particles can be de­ The major design aim of the grained matrix of scintillation count­ tected, the technique has an advan­ experiment is to study the structure ers and specially-developed drift tage over bubble chamber experi­ of the nucléon as revealed by the tubes to enable the development of ments where normally only charged weak neutral current. In these inter­ the hadron showers to be studied. particles can be traced and the effect actions the incoming The 25 metre-long detector is of neutrals has to be estimated. scatter elastically off the component built up of modules, each 4 m square In principle, the neutral current without changing their fla­ and containing a 3 m square marble reacts differently with up (u) and

CERN Courier July/August 1979 193 Apparatus of the 'CHARM' (CERN/Hamburg/Amsterdam/Rome/Mos­ cow) collaboration in the neutrino beam at the CERN SPS, now producing the first in what promises to be a fruitful series of results. On the right can be seen the downstream end of the CERN/Dortmund/ Heidelberg/Saclay detector. For measurements on polarization, these two mighty detectors join forces.

(Photo CERN 105.7.78)

down (d) type quarks, but this iso- The CHARM techniques of energy Again further data will be available dependence is not yet known. flow measurement are also useful in soon. This problem is sidestepped in muon studies as they allow the so- Another important result comes CHARM through the use of marble called leading muon' — the muon from the combined use of th target slabs, which contain even- produced directly by the incident CHARM detector and the 1200 ton even nuclei and so have equal neutrino — to be readily separated iron target-calorimeter of the CERN/ numbers of u and d quarks. Marble from additional emerging Dortmund / Heidelberg / Saclay was selected as the cheapest such subsequently from the hadron (CDHS) experiment immediately up­ target material which would also shower. stream. This combined experiment allow muon polarization measure­ As well as studying the hadron with 36 metres of equipment in­ ments. showers produced in neutral current stalled in the neutrino beam must First CHARM results, from a run interactions, the apparatus can also surely rate as one of the biggest last autumn, show that the nucléon be used to look at the purely leptonic assemblies of scientific equipment structure functions as measured by process of neutrino-electron scatter­ ever used in a single experiment. neutral currents are similar to those ing, where the recoil electron pro­ The idea is to measure the polar­ measured in charged current inter­ duces an electromagnetic shower ization of the muons produced by actions. More data should be avail­ close to the direction of the incident high energy charged current interac­ able soon and should give the spec­ neutrino. tions in the CDHS detector to ascer­ tra which show how the neutral Preliminary results on electron- tain whether the spin effects of weak current transfers energy to the target neutrino scattering are in good interactions at GeV energies are the quarks (the so-called y-distribu- agreement with the world average same as those known for twenty- tions), and comparison of these value for the 'Weinberg' mixing five years in beta decay and other spectra with those of the charged angle, and show well how this diffi­ low energy weak phenomena where current could provide new informa­ cult experiment can be handled the emergent lepton carries the tion on the neutral current. using an electronic calorimeter. same 'handedness' as the incident

194 CERN Courier July/August 1979 neutrino. Polarized targets and its resistance to radiation First results are averaged over the damage, could provide target mater­ angular and energy distributions of from ammonia ials considerably more effective than the emergent muons and show that those in common use. the conventional picture of spin Ammonia contains some 18 per At CERN, 2 mm diameter solid effects in weak interactions is still cent of hydrogen, more than that ammonia beads were exposed to a good — the first time that lepton found in propanediol and butanol, 580 MeV beam from the polarizations have been studied at the commonly used polarized target synchro-cyclotron (SC) with 1015 these energies. materials. This, together with its per cm2, considerably in Further progress lies in carrying relatively high solid density, means excess of what any polarized target out sensitive tests of the conserva­ that ammonia has considerable po­ has been exposed to so far. tion of handedness in situations tential advantages for polarized tar­ The beads were held in liquid where kinematics alone says that get experiments, but previous at­ nitrogen both during the irradiation the probability of conserved handed­ tempts to prepare polarized am­ and during their transfer to the dilu­ ness is strongly suppressed and monia samples have encountered tion refrigerator of the target. Nor­ where on the contrary the probability problems. mally radicals react very quickly, but of changing the handedness is Now a new technique developed at these temperatures the new radi­ enhanced. This occurs when the at CERN has shown that the chemi­ cals produced by the irradiation are muon produced by an antineutrino cal radicals produced by intense irra­ relatively inert, and their physical comes off backwards and all energy diation can produce proton polariza­ properties can be exploited for is transferred to the target . tions in ammonia of over 90 per cent, dynamic polarization. With this list of results already comparable to those obtained with Analysis of the samples by elec­ available from preliminary runs, the propanediol. This, together with the tron spin resonance shows the signs are that CHARM will go on to intrinsic advantages of solid am­ presence of these radicals, and it be a prolific experiment. monia as a polarized target material seems feasible that the radical concentration could be increased significantly before unwanted chemical destruction occurs. If this can be achieved, the homo­ geneity of the sample and its increased resistance to radiation could result in polarized targets many times more effective than those now in use. Further progress lies in finding the optimum method of irradiation and subsequent treat­ ment of the ammonia to produce the best polarization results.

A new technique developed at CERN has shown how significant proton polarizations can be produced in solid ammonia. Shown here is the NMR absorbtion line corresponding to a polarization level of 90 per cent The asymmetry, observed for the first time, shows that the polarization is indeed produced in the solid ammonia, and confirms that in previous work, the observed polarization was mainly due to the doping material.

CERN Courier July/August 1979 195