VELO upgrade: Requirements for Physics Performance 6/14/2016 LHCb VeloPix Module Kickoff Meeting 1 LHCb VELOPix Module Kickoff Meeting Nikhef – November 9 th 2009 Paula Collins

LHCb: The “Day 1” Experiment Mass resolution: 14 MeV Time resolution: 40 fs IP resolution: /p T  m PID over GeV ~ bb pairs produced per year Trigger goes from 40→1 MHz in hardware, then to 2kHz in software 6/14/ bb production correlated and sharply peaked forward-backward Single-arm forward spectrometer : mrad σ bb ~ 500 µb in LHCb acceptance Production of B +, B 0, B, b-baryons.., LHCb (will) run at L = cm -2 s -1 by not focusing the beam as much as ATLAS and CMS maximizes probability of a single interaction per crossing LHCb will go immediately to design luminosity LHCb in numbers LHCb VeloPix Module Kickoff Meeting

To extend the physics programme, why not just turn up L ? LHC is (will be) capable of delivering to LHCb ~50% of the L delivered to the GPDs – would be more than good enough! Baseline scenario: increase our luminosity from to 2x10 33 cm -2 s -1  Crossings with ≥ 1 interaction 10 MHz → 30 MHz  Average number of interactions per crossing 1.2 → 4.8  Spillover: increases linearly with L Compatible with SLHC I high x I low scenario 6/14/2016 BUT, it’s all about the trigger! Level-0: Largest E T hadron, e(  ) and  1MHz read-out rate is currently the bottle neck in the system  channels: yield proportional to L Hadronic channels: If we increase L we have to increase our E T cut and there is no net efficiency gain! Our current 2.5 us latency is inadequate for a trigger decision of this complexity LHCb VeloPix Module Kickoff Meeting 3

LHCb upgrade strategy = Move to a full software trigger 6/14/ The consequence: Read out all sub-systems at 40 MHz Replace all FE-electronics; all silicon modules, RICH-HPDs, FE boards of Calorimeter, Outer Tracker FE LHCb VeloPix Module Kickoff Meeting Trigger uses ALL event information, reconstructs all primary vertices, and can cut on p T for high i.p. Preliminary studies show that the hadron efficiency will improve by ~2, and yield will be proportional to L Increase in statistics x20 for hadronic channels and x10 for leptonic channels This gives the additional flexibility to adapt to the physics landscape in the next decade The idea The consequence Aim to operate at L = Perform entire trigger on CPU farm with input rate 30 MHz Goal is to double trigger efficiency for hadronic channels and make the yield scale with luminosity All subsystems must be fully read out at 40 MHz Replace most FE electronics, silicon modules, RICH HPDs, FE boards of calorimeter and outer tracker Case study: B s   (after HTL1) L = 2x10 32 cm -2 s -1 E T > 3.5 GeV   ≈ 22% Min.Bias retention 10 kHz L = cm -2 s -1 E T > 2 GeV   ≈ 45% Min.Bias retention 28 kHz

VELO: Current Design 6/14/2016 LHCb VeloPix Module Kickoff Meeting 5  2 retractable detector halves:  7 (37) mm from beam when closed (open)  21 stations per half with an R and  sensor  Operated in secondary vacuum  300μm Al foil separates detector from beam vacuum  Bi-phase CO 2 cooling system 5 RF foil modules Base Kapton cables Cooling manifold 5

VELO sensors 6/14/2016 LHCb VeloPix Module Kickoff Meeting 6 6 Ф measuring sensors:  2 regions  Short/long strips  Pitch=36-97μm  Stereo angle. 6 silicon edge just 7 mm from beam! R measuring sensors:  45 o quadrants  Pitch=40-102μm 512 strips 512 strips 512 strips 512 strips 683 inner strips 1385 outer strips 300  m n in n strip sensors (Micron Semiconductor) Double metal layer for signal routing

6/14/2016 LHCb VeloPix Module Kickoff Meeting 7 7 Operating up to ~120 fb -1 Flux: 0.8x10 14 n eq cm -2 per fb -1 TID (Electronics): 3.7 MRad per fb -1 at tip = 7mm 7 Upgrading the VELO: Irradiation issues Radius (cm) Dose after 100 fb -1 n eq cm -2 x TID (MRad) After this 900V we expect 102 uA / cm -2 at -25 o C CCE of ~ 8.5 ke - Thermal runaway at the tip is the issue tip of current VELO T. Affolder TIPP 09

6/14/2016 LHCb VeloPix Module Kickoff Meeting 8 8 Upgrading the VELO: Bandwidth The occupancy is relatively low, but at 40 MHz the data rates are enormous Rough estimate gives 5 Gbit s -1 per FE for current design Minimum of 1400 optical links needed for whole detector Clustering issues become very important for getting the data off-chip 8 Radius (cm) Particle Hits / Event / cm 2 Averaged over all sensors L = L = L = L = a  b  Dedicated R&D needed on High speed copper cables within tank Feedthroughs/PCBs

6/14/2016 LHCb VeloPix Module Kickoff Meeting 9 Radius of first measured point (mm) Original layout Effect of removing 10 stations The global constraint is the ~1.2 m length of the vacuum tank From our previous studies we know that the impact parameter resolution is well described to first order by 9 Upgrading the VELO: design issues Keep down material before the second measured point High momentum tracks: keep the first measured point as precise as possible (i.e. fine pitch and good position information Keep the extrapolation distance as small as possible: Many stations Curved inner shape Minimum inner radius Edgeless technology an advantage Remember though the radiation at the tip Behaviour of impact parameter resolution as VELO material is increased Behaviour of impact parameter resolution as foil material is decreased

10 Material Budget and Resolution Several issues regarding Material/Resolution are still on the table What is required for physics performance? X 0 and  will affect IP, P resolution and efficiency. Critical quantities are: The total amount of material before the second measured point Foil + station tip thickness The total amount of material in front of the rest of LHCb (secondaries, pattern recognition in RICH, ghost rate for strips) Station thickness, number of stations directly affects our acceptance. For example, Bs->DsK would have a reduction by 30% for a of 6% 10 Slope of this line ~ sqrt(material) Currently material = 2.3% foil + 0.6% silicon Also ~ - inner dimension very important - number of stations very important Also small effect from resolution High momentum part affected by resolution. After irradiation this will go binary and be given by the pitch 6/14/2016 LHCb VeloPix Module Kickoff Meeting

116/14/2016 LHCb VeloPix Module Kickoff Meeting 11 Ghost rate study in the VELO: Impact of material on ghost rate (for strips) Vladimir Gligorov Material Budget and Ghost Rate

6/14/2016 LHCb VeloPix Module Kickoff Meeting 12 Material Budget and Impact Parameter Resolution Varying Velo ThicknessVarying Foil Thickness

136/14/2016 LHCb VeloPix Module Kickoff Meeting 13 TIMEPIX Material Estimate: -150  m silicon + ASIC ~ 0.3% -100  m Aluminium ~ 0.2% -200  m Diamond ~ 0.2% -TOTAL ~ % per station (single layer) 21 stations as current VELO 8W per station datarates ~ 50 particles per event per station ~ > 60 Gbit/s/station Number of hits per track z of first measured point (compared to VELO with inner radius of 8 mm..)

Summary of Requirements Match 250 x 300 mrad LHCb acceptance Survive (or half survive and be replaced) upgrade irradiation levels Out gassing within range Provide a vertex trigger with acceptable timings For the pixel option, positioning accuracy is “relaxed” (what we have now probably is good enough) Material must be kept low. 1% OKish, but 30%. 6/14/2016 LHCb VeloPix Module Kickoff Meeting 14

Backup 6/14/2016 LHCb VeloPix Module Kickoff Meeting 15

6/14/2016 LHCb VeloPix Module Kickoff Meeting 16 July-August 2009: Dedicated Timepix Telescope A telescope was constructed with 6 double angled (at 9 o ) planes. 4 Timepix and 2 Medipix sensors were used. The DUT (in this case another Timepix chip) position and angle can be controlled by a stepper motor to reduce the number of interventions Thanks to our colleagues from the CMS SiBT and the EUDET-Spider collaboration who enabled us to run in the H6 and H8 120 GeV pion beams 6 plane timepix/Medipix telescope DUT

6/14/2016 LHCb VeloPix Module Kickoff Meeting 17

6/14/2016 LHCb VeloPix Module Kickoff Meeting 18 TIMEPIX example data with mips Mean value of cluster size varies from between 0-18 o Landau very clean; noise is negligible Precise tracking clearly picks out binary and charge sharing regions Landau peak, Timepix at 0 o Cluster size, Timepix at 10 o Track residuals Timepix at 6 o Example SPS Beam Profile in TIMEPIX chip

6/14/2016 LHCb VeloPix Module Kickoff Meeting 19 TIMEPIX and MEDIPIX charge sharing Charge Sharing Y axis: Track prediction X axis: cluster measurement (simple charge weighting) 9 degree angle10 degree angle6 degree angle MEDIPIX (binary) 10 o TIMEPIX (TOT)

6/14/2016 LHCb VeloPix Module Kickoff Meeting 20 Preliminary result: TIMEPIX resolution Estimated track contribution to residual Timepix: 55  m pitch Unbiased x Residual as a function of angle Rotation about Y axis PRELIMINARY: UNCALIBRATED DATA!!

6/14/2016 LHCb VeloPix Module Kickoff Meeting 21 Preliminary result: HV scans at angle Width of y residual Scanning the HV up and then down again shows a clear shift in the residual means for highly angled tracks 10 degrees 18 degrees Mean of x residual Mean of y residual (rotation is about y axis).. 18 degrees Width of x residual The residual width also shows a clear dependence on orientation. This is as expected, and illustrates the sensitivity of the measurement

Why upgrade? Or, Why Should We Fully Exploit LHCb b production? There are hints of NP being just around the corner. If they are confirmed by LHCb e.g. in B s →J/  then the path forward is clear and the precision measurements must be pursued If ATLAS/CMS discover NP, but the effects are more subtle in the flavour sector then we will need precise measurements to test predictions  Pursue channels statistically limited at current experiment e.g. Bs→   Keep pace with theoretical predictions which will improve with time e.g. e.g. indirect precision on         factor 5 better thanks to significant improvements from lattice QCD? arXiv: v33 6/14/ LHCb VeloPix Module Kickoff Meeting

Pushing the Precision Frontier  s =  rad one of the most precisely predicted CPV quantities in the standard model If NP in the B s sector turns out to be large, then LHCb upgrade will be needed If it turns out to be small (as appears to be the case in the B d sector) then precise measurement is needed to match clean prediction 6/14/2016 LHCb VeloPix Module Kickoff Meeting 23 LHCb ( J/   ) Upgrade ( J/   ) SM  0.01~ LHCb numbers are with J/  alone Precision will be even better with other channels e.g. J/  f o (  ) Direct proportionality to η leads to interesting constraint on UT LHCb precision, 10 fb -1

b→s penguins, a very promising place for NP to lurk B s 0 →  dominated by penguins: NP can enter in mixing box and/or in penguins CP violating asymmetry is zero, due to cancellation of mixing and decay phases 6/14/ LHCb VeloPix Module Kickoff Meeting Can be complemented by B 0 →  K s 0 and family: At the upgrade we expect events and a precision of 0.02 At upgrade 0.6M events and error of 0.01 Intriguing pattern emerging, but existing precision poor LHCb and upgrade will clarify this picture

B s →  and B d →  – an exciting future 6/14/2016 LHCb VeloPix Module Kickoff Meeting 25 SM prediction is precise, and small! This can be reached with 10fb -1 at LHCb. If NP gives significant enhancements then will be seen sooner! However: Certain models, e.g. MCPVMFV, can give enhancements but can also suppress the branching ration < SM depending on phases Need more statistics than available at baseline LHCb 10fb -1 to approach SM 10% precision Rate of (B d /B s )→  tightly constrained and can distinguish SM and MFV ( Buras: hep-ph/ ). Might B d →  be visible at upgraded LHCb??? Blanke et al, JHEP 0610:003, 2006

B → K 0* l + l - Powerful NP laboratory Host of interesting observables. Angular distributions e.g. forward-backward asymmetry of the angle between lepton and B in the dilepton rest frame Position of zero asymmetry crossing point will be measured by LHCb as well as needed, but many other theoretically clean observables will only come into play with > 10 fb M yield at upgrade 100 fb-1 6/14/2016 LHCb VeloPix Module Kickoff Meeting 26 With larger statistics, study of further observables (transverse asymmetries: A T (2), A T (3), A T (4) ) sensitive to NP Egede, JHEP11 (2008) 32

LHCb 10 fb -1 NP physics highlights 6/14/ LHCb VeloPix Module Kickoff Meeting Rare decays: B s  µµ Direct search for NP 3  measurement of SM prediction Mixing phase in B s  J/  (tree) Sensitive to NP in mixing Measure  (2  s ) ≈ 0.01 Mixing phase in B s   (penguin) Sensitive to NP in loops Measure 2  s eff ≠ 0 (=NP) with  ≈ 0.03 CKM angle  from  B d  D/DK, B s →D s K, B d - >D  (tree) standard candle against which NP sensitive measurements can be compared measurements to ~ 2° degrees CKM angle  from B d(s) → , KK (penguin), B→hhh  _NP  vs  _SM Sensitive to ≈ 3° degrees CPV in penguins B d   K s :  vs  eff Sensitive to NP in loops Sensitive to ≈ 0.1 Search for RH currents in radiative decays B s    ; Asymmetry FB of B d  K* µµ (zero of A FB (s) to 7%) D meson physics CP, D-D mixing Santos Reece, Belyaev Leroy Ricciardi Carson Magnin Leroy

LHCb 10 fb -1 NP physics highlights 6/14/ LHCb VeloPix Module Kickoff Meeting Rare decays: B s  µµ Direct search for NP 3  measurement of SM prediction Mixing phase in B s  J/  (tree) Sensitive to NP in mixing Measure  (  s ) ≈ 0.01 Mixing phase in B s   (penguin) Sensitive to NP in loops Measure phase ≠ 0 (=NP) with  ≈ 0.03 CKM angle  from  B d  D/DK, B s →D s K, B d - >D  (tree) standard candle against which NP sensitive measurements can be compared measurements to ~ 2° degrees CKM angle  from B d(s) → , KK (penguin), B→hhh  _NP  vs  _SM Sensitive to ≈ 3° degrees CPV in penguins B d   K s :  vs  eff Sensitive to NP in loops Sensitive to ≈ 0.1 Search for RH currents in radiative decays B s    ; Asymmetry FB of B d  K* µµ (zero of A FB (s) to 7%) D meson physics CP, D-D mixing, rare decays Santos Reece, Belyaev Leroy Ricciardi Carson Magnin Leroy Measure BR to ~5-10%, search for B d  µµ Improve by factor 3: Level of indirect prediction Measure to  ≈0.01, pin down NP sub-degree precision Improve by factor 4-5 Comparison at 0.03 o level New observables to improve NP sensitivty Measure and characterise CPV