BEAST results on SuperKEKB beam background: focus on the PLUME - - PowerPoint PPT Presentation

BEAST results on SuperKEKB beam background: focus on the PLUME pixelated system

Jerome Baudot

• n behalf of the BEAST/Belle II collaboration

➙Beam induced background at

SuperKEKB & Belle II: BEAST

➙The double-sided PLUME device ➙Single Beam background estimates ➙Outputs with 2-sided measurements

Belle II physics goals

• The intensity frontier
• Built up on B factories success
• e+e- coll. at (4s)
• integrated luminosity x 50
• Flavour studies
• New source of CP violations
• Lepton non-universality
• Charged lepton flavour violation
• Left-Right symmetry contribution
• Dark sector
• Complementary / LHCb
• Vertex Detector (VXD) Requirements
• Track impact parameters
• Goal s(high p) ~ 15 mm
• B, D, decay vertices
• Goal s ~ 60 mm
• 30 kHz trigger rate
• Innermost layer
• Hit rate >0.4 hits/mm2/s
• TID: 20 kGy/year

BEAST results on beam Background at SuperKEKB: PLUME focus -

• J. Baudot -

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early phase 3

See F. Luetticke’s talk from Monday 10th SuperKEKB

Phase 2

SuperKEKB collider

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HER: e- 7GeV e+ 4GeV :LER

Damping ring for low emittance e+

Positron source

low emittance e- gun Add / modify RF systems for higher beam current Higher e+ energy to mitigate Touschek bkg

Large currents

HER Ibeam = 3.6 A LER Ibeam = 2.6 A New final focusing magnets

New LER pipe

Nominal Lpeak = 8x1035 cm-2.s-1

e+ e-

Nanobeam scheme

Vertical beam size 60 nm

Crossing (Piwinski) angle =83 mrad to mitigate beamstrahlung

𝑀 ∝ 𝑂−𝑂+𝑔revol 𝜏𝑦𝜏𝑦 = 𝐽±±𝑧 𝜒𝜏𝑨𝛾𝑧

∗

The Belle II detector

BEAST results on beam Background at SuperKEKB: PLUME focus -

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An upgrade of Belle

Beam induced backgrounds

• Single beam effects
• Touschek  intra-beam scattering
• rate ∝

𝐽𝑐𝑣𝑜𝑑ℎ

2

𝑂𝑐𝑣𝑜𝑑ℎ 𝜏𝑦 𝜏𝑧 𝐹𝑐𝑓𝑏𝑛

3

=

𝐽𝑐𝑓𝑏𝑛

2

𝜏𝑦 𝜏𝑧 𝐹𝑐𝑓𝑏𝑛

3

𝑂𝑐𝑣𝑜𝑑ℎ

• Beam gas  vacuum residues
• rate ∝ 𝐽bunch × 𝑂bunch × 𝑄 𝐽
• Dynamic pressure 𝑄 𝐽 = 𝑞0 + 𝑞1𝐽𝑐𝑓𝑏𝑛
• Synchrotron radiation  magnet bending
• rate ∝ 𝐽beam
• Beam-beam effects (QED)
• rate ∝ Luminosity

BEAST results on beam Background at SuperKEKB: PLUME focus -

• J. Baudot -

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Radiative Bhabha scattering 2-photon interaction

sy << sz 

e+ e+ e- e- 

Beam induced backgrounds

• Single beam effects
• Touschek  intra-beam scattering
• rate ∝

𝐽𝑐𝑣𝑜𝑑ℎ

2

𝑂𝑐𝑣𝑜𝑑ℎ 𝜏𝑦 𝜏𝑧 𝐹𝑐𝑓𝑏𝑛

3

=

𝐽𝑐𝑓𝑏𝑛

2

𝜏𝑦 𝜏𝑧 𝐹𝑐𝑓𝑏𝑛

3

𝑂𝑐𝑣𝑜𝑑ℎ

• Beam gas  vacuum residues
• rate ∝ 𝐽𝑐𝑣𝑜𝑑ℎ × 𝑂𝑐𝑣𝑜𝑑ℎ × 𝑄 𝐽
• Dynamic pressure 𝑄 𝐽 = 𝑞0 + 𝑞1𝐽𝑐𝑓𝑏𝑛
• Synchrotron radiation  magnet bending
• rate ∝ 𝐽beam
• Beam-beam effects (QED)
• rate ∝ Luminosity

BEAST results on beam Background at SuperKEKB: PLUME focus -

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• Expectations
• Dominates beam lifetime
• Higher relative impact

at large radii (CDC, TOP)

• Sub-dominant
• Issue for innermost PXD

(mostly horizontal plane)

• Dominant at Lnominal
• Saturate VXD occupancy

Belle II in Phase 2

• BEAST goals
• Safe background conditions

for VXD insertion / phase 3

• Real-time background monitoring

during SuperKEKB tuning

• Understand individual

background components

BEAST results on beam Background at SuperKEKB: PLUME focus -

• J. Baudot -

PIXEL 2018

7 BEAST setup No final VXD

During Phase 1 (no collisions):

Initial measurements with another BEAST setup

The BEAST setup: complementarity

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Sensor Measurement

B-II PXD

DEPFET 2 ladders

In-situ occupancy tracking & vertexing

B-I SVD

DSSD 4 ladders

Diamond

8 sensors

Ionizing dose in VXD

FANGS

Hybrid pix (ATLAS) 3 ladders

Charged particle & X-ray synchroton rates

CLAWS

Scint.tile SiPM (ILC) 2 ladders

Rates with ns precision / injection

PLUME

2sided MAPS (ILC) 2 ladders

Rates & two-sided track.

MicroTPC

8 units

Fast neutron rate

He3 tube

4 units

Thermal neutron rate

Rad.Film

Many

Radiation level

PinDiode

80 units

Radiation at focus.magnet

Material budget Final VXD ~3.5 % X0 BEAST ~4.0 % X0

PLUME double-sided layer

• Concept
• Double-sided layer of pixel sensors
• Designed driven by ILC-VXD
• Air cooled
• Collab: Bristol, DESY, IPHC
• PLUME-2
• 2x6 MIMOSA-26 sensors
• Pitch 18.4 mm
• Binary output
• Thinned to 50 mm
• 8 Mpixels
• integration time 115 ms
• 2 mm thick Si-carbide foam
• Material budget 0.4% X0
• 4 ladders produced

BEAST results on beam Background at SuperKEKB: PLUME focus -

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Side view

PLUME geometry in BEAST

• 2 complementary angles
• 1350 & 225o
• Opposite to VXD sector (0o)
• Radius covered
• SVD range

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Phase 2 data taking

• SuperKEKB
• Started March  Ended July 2018
• Collimator adjustment and tuning
• 𝛾𝑧

∗ decreased from 8 to 3 mm (s*y ~ 400 nm)

• Beam current up to ~800 mA
• BEAST
• Permanent online monitoring during tuning
• dedicated study with varied: collimator, current, beam size, injection

BEAST results on beam Background at SuperKEKB: PLUME focus -

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11 Best peak lumi: 5.4x1033 cm-2.s-1

BEAM size PLUME CLAWS

Radiation levels

• From radiochromic films
• Decrease with radius in inner volume: ~1 kGy  few 100’s Gy
• Clear contribution from low penetrating radiations
• PLUME specific
• 99% up time during all Phase 2 period
• No significant sign of TID  crosschecked by radio.films (~200 Gy)

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Single-Beam background estimates

• Separate contributions

through their dependence to current and beam-size

• 2 absolute contributions to rate: T (Touschek), B (Beam-gas)
• T, B specific to each detector
• PLUME fit examples

BEAST results on beam Background at SuperKEKB: PLUME focus -

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13 𝑆𝑏𝑢𝑓 𝐽, 𝜏𝑧 = 𝑈

𝐽𝑐𝑓𝑏𝑛

2

𝜏𝑧 𝑂𝑐𝑣𝑜𝑑ℎ + B 𝑞1𝐽𝑐𝑓𝑏𝑛 2

+𝑞0 𝐽𝑐𝑓𝑏𝑛 LER

Ibeam (mA) Rate (particle/cm2/s)

Single-Beam background estimates

• Unknown additional contribution for HER
• For large beam size, rate rise again!
• Data favour a Touschek-like contribution
• Unclear origin
• Large beam tails

to account for it

BEAST results on beam Background at SuperKEKB: PLUME focus -

• J. Baudot -

PIXEL 2018

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𝑆𝑏𝑢𝑓 𝐽, 𝜏𝑧 = 𝑈

𝐽𝑐𝑓𝑏𝑛

2

𝜏𝑧 𝑂𝑐𝑣𝑜𝑑ℎ + B 𝑞1𝐽𝑐𝑓𝑏𝑛 2

+𝑞0 𝐽𝑐𝑓𝑏𝑛 + X

𝐽𝑐𝑓𝑏𝑛

2

𝜏𝑧

3 𝑂𝑐𝑣𝑜𝑑ℎ

HER

PLUME

Ibeam (mA) Rate (particle/cm2/s)

Single-Beam background findings

• PLUME data shown so far, but of course similar plots for all BEAST/Belle II
• Rates in inner volume during Phase 2
• Of course O(102) smaller than expectation for phase 3
• Dominated by LER wrt HER

 Additional collimators for phase-3

• Beam Gas  Touschek for PXD radii
• Beam Gas < Touschek for SVD radii
• Synchrotron radiation
• 1st observation (PXD, SVD, FANGS)
• X-rays in 8-15 keV range
• Not well reproduced in simulation
• Not seen in PLUME

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Sinlge-Beam background findings

• Comparison to simulation
• Dedicated beam simulation (SAD)

+ GEANT 4

• Relative rates (r, f) OK
• LER rates reproduced

within a factor 5-20

• HER rates not reproduced reasonably

Under investigation

BEAST results on beam Background at SuperKEKB: PLUME focus -

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16 PLUME preliminary

Beam Gas DATA/MC Touschek DATA/MC

Luminosity background ?

• Luminosity background
• Mostly e from interaction point (IP) at low momentum (< 50 MeV)
• pT > 15 MeV to reach PLUME (5 cm radius)
• “Tracking” with PLUME double-sided feature
• Associate nearest hits on both sides pointing to IP
• Bending & low p => dR< few mm & f~p/2

BEAST results on beam Background at SuperKEKB: PLUME focus -

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17 Inner side Outer side Beam axis Projected view f dR

rejected associated

PLUME

2 mm

dR

Luminosity background in MC

• Selections
• Sensors nearest IP along beam axis
• 2.0 < f < 1.4 Rad
• dR < 2 mm

BEAST results on beam Background at SuperKEKB: PLUME focus -

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18 Projected view f dR

f (Rad)

200 ms of Two Photon simulation  Efficiency on total # particles from luminosity background = (5  1) 10-3

• Combinatorial
• Ultra-dominant

in real data

Luminosity background in data

• Run with average luminosity 1.3 1033 cm-2.s-1
• After selection (dR< 2mm)
• After correcting for efficiency
• Background from luminosity

38  22 hits/cm2/s

• Hit rate / Lumi ratio agrees within 10%

between MC and data

BEAST results on beam Background at SuperKEKB: PLUME focus -

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19  Lumi. Background barely visible 160 to 650 x lower than Single Beam background

200 s of data taking 10 s of data taking

Preliminary

Summary

• Beam induced background from phase-2 (current status)
• Low enough to start operation of full VXD & Belle II in general
• Low Energy Ring contribution dominates High Energy ring
• Discrepancy with respect to current simulation

 under investigation

• Further background mitigation during early phase-3
• Dedicated devices: CLAWS, more Diamonds, pin-diodes, He3
• PLUME in BEAST
• Went through complete data taking during phase-2
• Still perfectly usable
• Double-sided feature provide 1st glimpse on luminosity-related background
• Negligible for lumi < 1034 cm-2.s-1 as expected
• Future of PLUME as a versatile double-sided pixelated system
• Current version exploits 10 years design
• Still proves very useful
• Needs upgrade with newest (fastest) thin sensors
• Demonstration of longer ~50 cm range close to 0.3 % X0

BEAST results on beam Background at SuperKEKB: PLUME focus -

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Additionnal slides

➙SuperKEKB & Belle II ➙MIMOSA-26 sensors ➙PLUME design ➙BEAST phase 1 ➙More on BEAST phase 2

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SuperKEKB nominal parameters

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Collimator at SupeKEKB

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LER(9):

• 7 horizontal, 2 vertical “SuperKEKB type” collimators
• horizontal: D06H1, D06H3, D06H4(*), D03H1

D02H1, D02H2, D02H3, D02H4

• vertical: D06V2, D02V1

HER(20):

• 3 horizontal, 1 vertical “SuperKEKB type” collimators
• horizontal: D01H3, D01H4, D1H5
• vertical: D02V1
• 8 horizontal, 8 vertical “KEKB type” collimators
• horizontal: D12{H1,H2,H3,H4},D09{H1,H2,H3,H4}
• vertical: D12{V1, V2, V3, V4},D09{V1,V2,V3,V4}

(*) D06H4 is moved to D06H1

29 movable collimators in total (6 are added after phase2)

From Hiro Nakayama

Phase 2 achievements

BEAST results on beam Background at SuperKEKB: PLUME focus -

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24 From Akio Morita

Vertical beam size Phase 2

BEAST results on beam Background at SuperKEKB: PLUME focus -

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25 From Salvatore Di Carlo

Beast setup

BEAST results on beam Background at SuperKEKB: PLUME focus -

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sensor contact p. number location DAQ unique measurement Tasks/ Priority Belle II PXD

• C. Marinas

2 ladders VXD Belle II / VXD EPICS in-situ occupancy, full Belle II tracking, vertexing 1,2 (4) Belle II SVD

• K. Nakamura

4 ladders VXD Belle II / VXD EPICS diamond sensors

• L. Vitale

8 diamonds VXD Belle II monitor DB & BEAST EPICS ionizing dose in VXD  BEAM abort 1,2 (4) FANGS “LHC style” silicon pixel sensors

• C. Marinas

3 arms 15 chips VXD BEAST EPICS MIPs & x-rays > 10 keV @ 40 MHz  Synchrotron x-ray spectrum 1,2,4 CLAWS Scintillators w/ SiPMTs

• F. Simon

2 ladders VXD BEAST EPICS X-rays or track counting w/ 1-ns timing  injection background 1,2 (4) PLUME “ILC style” silicon pixels sensor

• I. Ripp-

Baudot 2 ladders VXD BEAST EPICS Two-sided silicon pixels  tracklets w/ pointing 1,2 (4) Scintillators + PIN diodes

• H. Nakayama
• K. Nakamura

40+40 around QCS BEAST EPICS X-ray and total loss distribution versus position,  collimator adjustment 3 Micro-TPC nuclear recoil detectors

• S. Vahsen

8 VXD dock BEAST EPICS fast neutrons: rate, directional & spectral information 4 He-3 tube neutron detectors

• S. De Jong

4 VXD dock BEAST EPICS thermal neutrons: rate 4

From Sven Vahsen

CMOS pixel sensor in PLUME

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• MIMOSA-26 (2008)
• AMS 0.35 µm, resistivity > 0.4 kΩ.cm
• Sensitive layer: ~15 µm thick
• Power dissipation 350 mW/cm2
• Spatial resolution ~ 3 µm

Design Concepts: assembly

• Step 1
• Aligning & gluing sensors to FPCs
• Automatic placement machine
• Step 2
• Wire bonding on individual FPCs

➡️ 2 Modules

• Step 3
• Gluing 2 modules

simultaneously

• n both sides of a SiC foam
• Manually with a dedicated

jigs ➡️ 1 Ladder

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Module assembly robot Ladder assembly jigs

PLUME material budget

• PLUME-1 : 0.6 % X0
• PLUME-2 : 0.35 % X0

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Spatial & angular distributions

• PLUME-1

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Normal incidence

• L. Cousin (IPHC) thesis

PLUME DAQ/Control system

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31 From Gilles Claus

PLUME 3D model

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PLUME Irradiation during Phase 2

33 Fakerate increase by a factor 1.1 to 2.4 => Cumulated ionizing dose < 3 kGy Assuming a linear dependence between fake rate and TID (known to be wrong), TID ~ 0.9 kGy

• Fake rate increase factor:

○

In average 1.6

○

Std deviation 0.4

BEAST setup during Phase 1

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Beast Phase 1 methodology

BEAST results on beam Background at SuperKEKB: PLUME focus -

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35 From Peter Lewis

Phase 1 findings

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36 Touscheck Beam Gas => doi.org/10.1016/j.nima.2018.05.071

Fit with SVD rates at beam size scan

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• Extracted beam-gas and Touschek

coefficients, extrapolated to Phase 3. Large discrepancies between Data and MC, especially in HER. Same/similar pattern in

• PXD. To be investigated further why we see

such discrepancies. It is notable that our SAD loss rate in HER is much smaller than LER, almost zero.

Preliminary Preliminary

From Hikaru Tanigawa

Synchrotron radiation

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• PXD (ring outer side) and FANGS (ring inner side) see photon peak around 10keV
• Longitudinal distributions for HER and LER suggest same mechanism of SR generation

Most probable hypothesis: Photons produced in the Final Focus magnet are reflected on the Ta part of the pipe and reach the +X side of the IR. From Hiro Nakayama