Oxford Group LHCb and CLEO-c Report

Why flavour physics matters Status of LHC, LHCb and Oxford group RICH activities Physics activities (including CLEO-c) Summary and Outlook

Guy Wilkinson, Project Review, 1/10/07

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Importance of Flavour PhysicsFlavour physics has been an essential tool in construction of SM:

• GIM mechanism → charm• CP Violation → 3 generations• B mixing → heavy top

All surprises that predated‘direct’ discovery!

We may assume same story will continue. Precise measurements of low energy observables, eg. B-decays, a priori expected to revealpresence and nature of new physics at TeV scale and beyond.

In B physics goal is to look for new sources of CP violation, or deviations from SM in very rare CP conserving processes, eg. BR(Bs→μμ)

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‘Flavour facilities’, eg. LHCb, can make similar studies in D decaysand search for LFV τ decays – very wide physics programme.

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A topical example: D mixingMost interesting result in HEP in 2007 was first observation by BaBar and Belle of D mixing (characterised by x=Δm/Γ and y=ΔΓ/2Γ)

BaBar Wrong Sign Kπ analysis Combined BaBar/Belle allowed x-y contours

Immediate consequences for SUSY, eg. “it the first 2 generations of squark doublets are within reach of LHC, they must be quasi degenerate” Nir, arXiv:0708.1872v1

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LHC StatusLast dipole lowered April 26th this year !(First was in March 2005)

Last official schedule (August ’07) had beam commissioning beginning inMay ’08, with then 2 months estimated before first 14 TeV collisions

Since then, there have been problems,eg. with shielding bellows in cold interconnects

Warm up of sector 7-8

So knock-on delays not unexpected…

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Interaction point

LHCb Status

A very full IP8 - installation is very nearly complete &commissioning is underway

Schematic of what we arelooking at (but note the parity transformation)

Interaction point

RICH 1

RICH 2

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Group Status

Faculty: N. Harnew & G. Wilkinson Dept. Lecturer: J. Libby Royal Soc Fellow: Malcolm John Postdocs: R. Muresan & P. Spradlin Students: A. Powell, S. Brisbane, L. Martin, F. Xing,

Philip Hunt and Chris Thomas (joint with RAL) Electronics, Systems and Software Engineers:

I. McArthur, P. Sullivan, S. Topp-Jorgensen RICH 1 Mechanics : T. Handford, B. Ottewell, R. Senanayake Grid programmers: A. Soroko

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Oxford LHCb RICH Activities

Oxford group leading player in LHCb RICH since the beginning.

Current responsibilities:

RICH Project Leader (Neville Harnew)

and activites:

• RICH Level-0 Electronics

• RICH-1 Mechanics

• RICH calibration strategy (with real data)

RICH software coordinator (Guy Wilkinson)

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Status of the L0 electronics

Oxford’s responsibility is the front-end electronics for the RICH detectors

Hybrid Photo-Detectors (HPDs) detect the Cherenkov radiation by detecting photoelectrons on a 32×32 pixel detector encapsulated within the detector

readout pixel chip

silicon detectorSchematic of a HPD section

72 mm

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Level-0 Production & DAQ status

300 boards have been produced and tested in Oxford 242 boards required to equip

both RICHes Project finished successfully [on

time and within budget] Commissioning is in progress – all

RICH2 photon detectors have been successfully read out under HV

Final Level-0 experimental control system (ECS) is very well advanced at CERN

Sean Brisbane Neville HarnewJim LibbyPhil Sullivan Stig Topp Jorgensen

PIXEL anodes

Level-0 board

Kaptons

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Testbeam evaluation of 48 HPDs in 60 GeV/c beam with C4F10 radiator.

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L0 Readout in Action

(Beam single particles with composition 80% , 10% e, 7% K, 3% p)

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HPD column mounting at CERN

Sean Brisbane Andrew PowellPhil Sullivan

All RICH-1 and RICH-2 ladders are now fully equipped with HPDs and Level-0 boards

HPDs

L0 boards

RICH 2

RICH 1

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RICH1 mechanicsOxford has extensive involvement in RICH1 mechanics project, vital to the collaboration for delivering on time-critical items. Work in collaboration with ICSTM.

There will be pressure on Drawing Office and MechanicalWorkshop time until the end of the year.

Oxford produced final design and supervised construction of the RICH1 gas enclosure. This is now installed in LHCb pit.

Designed mechanical support and lifting rig for gas enclosure.

Designed and constructed mirror installation & storage boxes

Designed and supervised fabrication of upper HPD mounting and rail system. Still underway (until Nov).

Responsible for design and construction of the lower HPD mounting system. Still underway (until Dec).

Matthew Brock, Charlie EvansWing Lau, Brian OttewellTony Handford, Rohan Senanayake,Mike Tacon and the workshop team

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RICH-1 schematic

RICH-1 gas enclosure (installed with mirrors)

RICH-1 upper HPD rail system

RICH-1 lower HPD mounting system

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Particle Identification Calibration

Using MC truthUsing D* events

Kaon momentum [GeV/c]

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Use high statistics D*→D0(Kπ)π sample selected through kinematics alone (RICH unbiased) to calibrate performance of PID

RalucaMuresan

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Oxford and LHCb PhysicsOxford has had leading involvement in physics studies of LHCb flag-ship measurements since start of collaboration, and this continues.

• CP Working Group Convenor – Guy Wilkinson

Involves not just running MC studies on established methods, but developing new strategies to extend ‘physics-reach’ of experiment.

At present, tightly-focused and intensive programme in two key areas:

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1) Precise measurement of the unitarity triangle γ (LHCb’s raison d’etre ?)

2) Studies of charm mixing and search for CP violation in the D system.

[Libby, Harnew, Wilkinson, Powell, Brisbane, Martin]

[Wilkinson, Spradlin, Xing, Muresan]

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Oxford LHCb and the UT Angle γ

Best way (statistically precise and theoretically clean) to measure γ is through ‘B→DK’ decays.

Compare rates or kinematical distributions (eg. Dalitz plots) betweenB+ and B- for cases where f is a final state common to D and Dbar.

Eg. KK ππ

KsππKπππ

KKππKππ0

Interference term picks out γ, but also CP conserving phase between the D and Dbar decay (or in 3 and 4 body case, phases associated with eachintermediate resonance). If we know/can fit this (these), we get γ.

γ is essentially the CP violating phase in b→u transitions. It is very badlyknown (σ~ 300) from B-factories. A precise measurement of γ is the next big challenge in flavour physics. Oxford LHCb is leading this work.

We estimate combined precisionof 1-2o possible at LHCb !

γ

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0D 0D

0even-CPD 0

odd-CPD

B→DK measurements: the fly in the ointment

Take B→D(Ksππ)K as example. For γ extractionwe need to understand amplitudes and phasescontributing to Ksππ decay.

Dalitz plots for D→Ksππ

Can be modelled and fitted against decays of flavour eigenstates(available at BaBar/LHCb) but at expense of big systematic:

σγ (model) ~ 12o (BaBar)

No good for LHCb !

Work-around: look for orthogonalinformation to complement that which comes from flavour-tagged decays. Answer: decays of CP-eigenstates. But these not available at BaBar/LHCb…

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Oxford LHCb and CLEO-cCLEO is the grand-daddy of flavourphysics, with history of achievementdating back over 20 years.

Cornell University, Ithaca NY, USA

CLEO-c is latest incarnation.Dedicated programme of data-takingat and above the ccbar threshold, toperform studies needed for B physics.

Oxford LHCb physicists (with Bristol)have joined CLEO-c in order to measurequantities essential for our γ studies

Oxford student (Andrew Powell) on LTA

Recently had RRA bid approved by grants panelfor postdoc and travel funding to execute our programme

CESR

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CLEO-c: double tagged ψ(3770) events

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CLEO-c will collect >800 fb-1 at the ψ (3770)

DDbar produced in quantum entangled state:

Reconstruct one D in decay of interest for γ analysis (eg. Kπππ), & other in CP eigenstate (eg. KK, Ksπ0 …) then CP of other is fixed.

Thus we accumulate a clean dataset of CP-tagged decays with which wecan constrain amplitudes & phases in multibody D decays, and essentiallyeliminate limiting systematic errorfrom LHCb γ analysis !

Data: K3π vs Kπ

Note: very, very clean !

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Oxford LHCb and charm physics

Benchmark analysis: look for oscillatory component in ‘wrong sign’D→Kπ decays. Oxford pioneering study:

• In 1 yr will get >10x sample of both B-factories integrated over all time

• Methods developed for reconstructing D0 proper time with necessary precision

Conclusions: 1) LHCb can measure D mixing parameters (x and y)very precisely – interesting ; 2) LHCb has unprecedented sensitivity to CPV in charm decays and mixing – very interesting.

Oxford first group in LHCb to identify potential and importance of charmphysics measurements. (Recognised in RRA award in ‘round before last’)

• Bottom line: SM predicts ~ zero CPV ; many NP models don’t.

• It has certainly become very topical: observation of mixing this year by B-factories at very top end of SM expectation. Opens many possibilities.

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Summary and Outlook• Oxford efforts have been central to getting LHCb RICH system built and ready for data-taking (continued lab support for RICH 1 mechanics, DAQ and electronics necessary).

• LHCb physics programme is of highest scientific importance. All measurements will begin in earnest as soon as machine and detector is commissioned. We do not need LHC ‘1034’ operation.• Oxford in poll position to steer several of most important analyses, in particular γ measurement and charm studies.

• Entry into CLEO-c has allowed us to tackle vital challenges in the γ analysis prior to arrival of first LHC data.

• Finally: discussions underway for LHCb upgrade. Oxford are well placed to take place in electronics development for new RICH & trigger.

We live in exciting times for flavour physics. Appointment of a newacademic will ensure Oxford retains its current lead. Optimal timing would be as soon as possible, so to have maximum impact on LHC data analysis.