+ T

Robert Thorne

September 17th 2019

University College London

With thanks to Alan Martin

WJSIPPP – Sept 2019

Late 1990s – an expanded collaboration.

WJSIPPP – Sept 2019 1

The types of data sets were ever expanding. Could now start to makesome attempts at investigating “model uncertainties”.

WJSIPPP – Sept 2019 2

Detailed studies of a number of types of variation, e.g. cuts, αS(M2Z) ....

Comparison with the “Competition”.

WJSIPPP – Sept 2019 3

Further updates led to a detailed prediction study, and the firstappearance of a familiar plot (devised by James and shown usingupdated version).

WJSIPPP – Sept 2019 4

First inclusion of QED in availablePDFs.

Modelled photon input from evolutionfrom low-Q2 valence quarks.

Similar in principle to modern version.

Isospin asymmetry in valence quarksautomatically in right direction toreduce NuTeV anomaly.

R− =σνNC−σν̄NCσν

CC−σν̄

CC

= 12−sin2 θW−(1−7

3 sin2 θW )[δUV ]−[δDV ]

2[V −].

WJSIPPP – Sept 2019 5

First produced PDFs with approximateNNLO in 2003. OK, due togood approximations to NNLOsplitting functions.

First “full” set with heavy quarkthreshold properly included.

Also differential distributions forDrell-Yan included.

Full dependence in both rapidityand αS(M2

Z).

WJSIPPP – Sept 2019 6

WJSIPPP – Sept 2019 7

Used dynamical tolerance for thefirst time.

Also extended parameterisation fore.g. gluon.

WJSIPPP – Sept 2019 8

Studies of various issues suchas inclusion of jets or not.

Also variation of PDFs withscale, or jet algorithm.

WJSIPPP – Sept 2019 9

Again look at implications, and full comparison with older PDF oralternative sets.

Also the first appearance of another of James’ “standard” plots.

WJSIPPP – Sept 2019 10

MSTW produced PDFs with αs(m2z) uncertainties and in fine binned

variations in αs(m2z).

As always looked particularly at the implications.

WJSIPPP – Sept 2019 11

Also examined different flavour scheme numbers. James looked in greatdetail at how these affected LHC predictions.

WJSIPPP – Sept 2019 12

Final article with PDF determinations. As always James was askingadditional questions.

Improved valence parameterisations fit lepton asymmetry better. Whatabout interpretation and interesting predictions?

WJSIPPP – Sept 2019 13

James was interested in and contributed so much to, the study of PDFsfor their own sake.

(Note – I have essentially “ignored” two 500+ cited articles.)

However, also very much because they were fundamental to lots ofparticle physics.

Typical of his wide interests and expertise in particle physics andbeyond.

He made enormous contributions to the whole world of particle physics,physics and the scientific/academic world in general.

Always kept up with latest developments in PDFs.

WJSIPPP – Sept 2019 14

Photograph taken at Alan’s 80th birthday celebration in Durham.

WJSIPPP – Sept 2019 15