peter, the itc and the heavy flavors

Peter 70's birthday 2009

Peter, the ITC and the Heavy Flavors

¿ El ALEPH? -repetí.Sí, el lugar donde están, sin confundirse, todos los lugares del orbe, vistos desde todos los ángulosFrom El Aleph, J.L. Borges

”Aleph? ” I repeated. Yes, the place where they are, without confusion, all the places of the world, viewed from all angles


Aleph was a gifted Collaboration also because there were few high charismatic people capable to indicate the direction of the path to the success of the experiment and to inspire the young fellows.

Peter was one of those people.


Brief history of ALEPH and Peter

• The Collaboration was initiated in 1980 and is still producing papers.

• More than 30 institutions from western Europe, USA and China

• Took data at LEP from 1989 to 2000• Produced some 300 papers, 21 with more than 100 citationsPeter joined the ALEPH collaboration in 1983 after the demise of ELECTRA. He inspired the design of its Inner Trigger Chamber and directed its construction, in ALEPH he served as Spokesman, Chair of the Institution Board and Chair of the Editorial board.At Imperial we had worked hard for ELECTRA but realism had caused

us to examine the other experiments should there be disappointment.

Which of them had the same basic physics goals, which had a niche where our expertise would be valuable? Aleph satisfied both goals

and the niche we saw was the tracking area close to the interactionpoint, building on the two wire chambers we had produced for TASSO.


The Design of the ITC

At that time there was the reasonable fear that TPC could not work close to the beam line because of possible problems with space charge. In addition the TPC had a very long drift time, and could not be used for triggering. The proposal of the Imperial College group was to build a wire chamber that could satisfy the the following requirements:

Provide tracks for the 1st Level TriggerProvide tracking from the beam pipe to the first TPC pads at 30 cm radius.


The ITC Tracking

The ITC was a 2 m long chamber with axial wires which provided up to 8 accurate r-ϕ points.

For the trigger, the r-ϕ coordinate is given by the wire number and the z by the time difference of the arrival time at the two ends of the wire.

The tracking resolution in r-ϕ was 100 μmand the z resolution was 3 cm.


ITC Triggering

The ITC was able to trigger both in r-ϕ and in r-z. But the r-ϕ was more critical for the performance. The trigger information was selecting tracks with momentum > 1 GeV and was selecting the ECAL sector that the track could reach. This was the ALEPH main trigger.

With the exception of purely neutral final states the ITC trigger fired for virtually every interaction used in Aleph results. ALEPH PERFORMANCE PAPERLeptonic events have a lower multiplicity than hadronic events, and so require larger redundancy. For muons three triggers are used: the muon-track, electron-track, and back-to-back triggers. [ALL BASED ON ITC] The combined efficiency of these triggers is very near to 100%; the first is measured to be larger than 99.8% and all three of these triggers are present in more than 98% of muon pair events. The same triggers are used to select tau events, again achieving close to 100% efficiency.


Peter and ITCITC was responsibility of a single institution ….

At the end of ALEPH operation 945 of 960 wires were still operational and no wire broke.

No more than 10 days of run were lost in more than 10 years because of ITC problems.

BILL, Geoff, Ray, David, Marco, Dave, Roger, Dave, Ann, Dave, Julia, Andy.

…… and Peter was identifying ITC, the ALEPH Imperial College group and himself as one unique entity. It was (in) the center of ALEPH.


Peter and Bill in ECHENEVEX

July 1996


ITC Installation 26 Oct. 1988

ALEPH Note 82-91The whole operation turned out to be rather tense. One of the problems was the large number of people present, with ill-defined roles.


Had Peter ever a doubt on the ITC ?

………………………

The truth is that Peter always suffered when comparing the 21 TPC space points with the 8 ITC r-phi points !


ALEPH Event Display


Peter in between Online and OperationIn the beginning of 1989 the ALEPH control room was organized in two kingdoms: Online and Operation. The former responsible of collecting the data and putting them to tape, the latter responsible for all aspects of data monitoring and run organization.

The ALEPH spokesperson and founder – a very wise and strong man – had designed the managerial structure and chosen the main (also strong) characters. Unfortunately the interface was not working and ALEPH was not in condition to collect data smoothly.

.


Peter in between Online and OperationI remember a secret meeting (May 1989 ?) with Jacques, Lorenzo, Klaus, Peter and myself where we concluded that something had to change and proposed the figure of “Run Coordinator” to govern the two kingdoms. Peter was selected by us to be the first Run Coordinator.There was only one small detail: we had to communicate this decision to Jack. It was at that moment that I understood why I (young and inexperienced) was called in that meeting. The four old men looked at me and said: you go.


The first Z: 14th of July 1989Peter did a remarkable job in reconciling the different characters and in building up the correct team spirit that lasted for 10 years in the ALEPH control room.

ALEPH was ready for the pilot run that showed the readiness of the ALEPH tracking detectors that were able to measure the first Z at 13h15 of the first day of beam.

At the first CERN seminar ALEPH reported the number of neutrinos with a luminosity error of 2%, compared to 5% of OPAL and DELPHI and none of L3.


Peter and the Z lineshape

His only interest was to collect data at the peak at the highest possible rate and to measure heavy flavors with ALEPH.

And this is a remarkable story of some 10 publications in two years produced by the ALEPH Heavy Flavor group led by Peter.

In a nut shell: he could not care less.

Robert, Alain, Pierre, Roberto, Vivek, Dave, Roger, Paul, Marcello………


Early ALEPH Publications on HF

Heavy Flavor Production In Z Decays.TOPCITE = 100+Measurement of B - anti-B mixing at the Z.TOPCITE = 50+Measurement of the B hadron lifetime.TOPCITE = 50+Measurement of the forward - backward asymmetry in Z ---> b anti-b and Z ---> c anti-c.TOPCITE = 50+Production and decay of charmed mesons at the Z resonance.TOPCITE = 50+Evidence for b baryons in Z decays.TOPCITE = 50+Measurement of B - anti-B mixing at the Z using a jet charge method. TOPCITE = 50+Observation of the semileptonic decays of B(s) and LAMBDA(b) hadrons at LEP.TOPCITE = 50+Updated measurement of the average B hadron lifetime.TOPCITE = 50+


HF Identification

After R_L cut


Measurement of Rb

where the systematic error is dominated by the knowledge of the blepton B.R.

High or vs p fit ? This was the the question most asked by Peter in the HF meetings 1

submitted 25/4/1990

with electrons


ICHEP 1990 Singapore

high pt-leptons


ICHEP 1990 Singapore

First precise measurement of χ at LEP

Peter 70's birthday 2009 submitted 20/12/1990

The French fit :

Probability to PB


Measurement of the FB Asymmetry

submitted 23/4/1991

High Pt sample


Measurement of the FB Asymmetry

submitted 23/4/1991

The big fit in pt and p


Asymmetry today

20 times smaller than the early measurements


ITC measures the b-hadron lifetime

impact parameter divide by error


Early Aleph days

1986


CERN February 1991


Bari 1995


… all nice stories have an end

…. also ALEPH….

…..but memories stays forever in our heart……

peter, the itc and the heavy flavors

Documents

aleph collaboration

s birthday

borges aleph

aleph results

itc trigger

aleph main trigger

brief history of aleph

itc trackingpeter