Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8 th September 2004 p. 1 inear Collider Flavour Identification (LCF - Part 1 - S. Hillert (Oxford) on behalf of the LCFI collaboration Bristol U, Lancaster U, Liverpool U, Oxford U, RAL PPRP open session, London, 8 th September 2004 Overview Physics Studies Thin Ladder R & D
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Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8th September 2004 p. 1
Linear Collider Flavour Identification (LCFI) - Part 1 -
S. Hillert (Oxford) on behalf of the LCFI collaboration
Bristol U, Lancaster U, Liverpool U, Oxford U, RAL
PPRP open session, London, 8th September 2004
Overview
Physics Studies
Thin Ladder R & D
Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8th September 2004 p. 2
Introduction There is consensus in the High Energy Physics community that a TeV
scale e+e- linear collider (LC) has the first priority for the next major particle
accelerator, to operate with significant overlap with the LHC:
• “Reviews … point … to the conclusion that there is fundamentally new physics in the
energy range just beyond the reach of existing colliders.” (ICFA statement ’99)
• “The LC will extend the discoveries [to be made at the LHC] and provide a
wealth of measurements that are essential for giving a deeper understanding of
their meaning” (LC consensus document, 2004)
With the decision on the accelerator technology announced on 20 August,
world wide R&D effort will increase in speed and international collaboration
will intensify to reach a final design of the accelerator and the detectors.
“This is an extremely significant milestone. …
The UK should take a leading role in this one-off, global machine” (Ian Halliday)
Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8th September 2004 p. 3
The detector at the ILC
Compared to physics at the LHC, events at the ILC will be much cleaner;
much lower rates and background, known initial state;
Combining information from different subdetectors, we attempt to fully
understand the basic physics process on an event by event basis.
Requirements:
• continual, triggerless readout
• hermeticity
• highly granular tracking and calorimetry,
both inside a coil providing a high B-field
to resolve jets in multijet topologies
• vertex resolution for flavour identification
Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8th September 2004 p. 4
Application of a
particle flow algorithm
permits resolution of
events into the
jets corresponding to
the underlying quarks.
Use of the vertex detector permits us to distinguish the jets
generated by heavy quarks.
An example: e+e- t t
a typical e+e- t t event:
b
e+ e-
t
t
W
W+b
e.g. cq’ q’
s
qqe.g. s c
Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8th September 2004 p. 5
Vertex detector contribution to event reconstruction
The most interesting new processes (Higgs, SUSY, …) will be rich in heavy quarks.
Vertex topology and
effective mass of decay products
allows us to distinguish between
b and c jets.
Vertex charge allows us to
distinguish between quark and
anti-quark: b and b or c and c.
Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8th September 2004 p. 6
The LCFI R&D program
The linear collider flavour identification (LCFI) collaboration formed in 1998.
Since then we have carried out an extremely successful R&D program, aimed at finding viable
solutions for building a vertex detector whatever the machine choice would turn out to be.
The prototypes of sensors and readout chips developed by the end of the current funding
period would already have covered the major design specifications required by the warm
technology.
For the cold option, now chosen, we have developed two baseline designs, one of which
only emerged end of last year (cf. talk by Konstantin Stefanov).
The evaluation of which of these will be better matched to the requirements will need
further intensive R&D in close collaboration with international partners in academic
institutes and industry.
The LCFI program covers three closely connected areas of R&D:
physics studies, thin ladder R&D and detector development. The remainder of the
presentation will summarise our progress and future plans in each of these fields.
Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8th September 2004 p. 7
LCFI Physics studies
base, from which R&D goals are defined:
• How far do detector parameters like pixel size, ladder thickness, beam pipe radius,
readout time etc. need to be pushed for the measurements planned at the LC?
• What performance do the parameters which are technically achievable yield?
SLD experience: vertex detector is a powerful tool, crucial for LC physics goals;
besides b tagging it will allow
• high purity charm tagging (cf e.g. ICHEP’04 contribution 12- 0438)
provides a handle to unique physics in the TeV regime, complementary to LHC,
e.g. precision measurement of branching ratios in Higgs decays
• via vertex charge reconstruction: distinguishing between b and b, c and c
suppression of combinatorial background in multi-jet events
asymmetries: parity of Higgs boson;
CP asymmetries in SUSY processes
Bristol U
Lancaster U
Oxford U
RAL
Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8th September 2004 p. 8
Detector dependence of vertex charge reconstruction
“standard detector” characterised by: good angular coverage (cos = 0.96)
proximity to IP, large lever arm:
5 layers, radii from 15 mm to 60 mm
minimal layer thickness ( 0.064 % X0 )
to minimise multiple scattering
excellent point resolution (3.5 m)
standard detector is compared to
degraded detector: beam pipe radius 25 mm, 4 layers only; factor 2 worse point resolution
improved detector: factor 4 less material, factor 2 better point resolution
Vertex charge reconstruction studied in at ,
select two-jet events
Sonja Hillert, University of Oxford PPRP open session: LCFI, London, 8th September 2004 p. 9
Definition of vertex charge and of Pt-corrected mass
need to find all stable B decay chain tracks – procedure:
run vertex finder ZVTOP: the vertex furthest away
from the IP (‘seed’) allows to define a vertex axis