VELO Upgrade-II studies and information

This  page collects information on studies and presentations relating to the prospective Upgrade-II Vertex Locator, to be installed in LS4 and operate during LHC Runs 5 and 6.

 

  Approved figures and plots for presentations Up2FiguresAndPlots

 

 

 

This upgrade aims to  collect data at a factor 5-10 larger instantaneous luminosity in the HL-LHC phase, which will lead to a corresponding increase in the radiation dose, particle and vertex multiplicity.

For general information on the background, aims, and parameters of the project, the following links may be useful.

• Jan 2022: Considerations for the VELO detector at the LHCb Upgrade II 
• Jan 2019: Luminosity Scenarious for LHCb Upgrade II  
• May 2018: Physics case for an LHCb Upgrade II  
• Feb 2017: Expression of Interest for a Phase-II LHCb Upgrade: Opportunities in flavour physics, and beyond, in the HL-LHC era 

 

We have an e-group: lhcb-velo-upgrade2@cern.ch (archive)  

See also the general Upgrade-II tracking page .

 

Presentations

TTFU (Think Tank for Future Upgrades) Meetings

• Feb 2015, TTFU CERN. agenda 
  • Slides from P. Collins (overview) 
• Apr 2015, TTFU during A&S week. agenda 
  • Slides from V. Gligorov (PV association and timing) 
• Apr 2016, 1st Workshop on Future Upgrades, Manchester. agenda 
  • Slides from P. Collins (overview) 
  • Slides from J. Harrison (Toy and Full MC studies) 
• Jul 2016, TTFU CERN. agenda 
  • Slides from M. Williams (Toy and Full MC studies) 
  • Slides from P. Collins (ASIC considerations) 
• Oct 2016, TTFU CERN. agenda 
  • Slides from M. Williams (short overview) 
  • Slides from M. Jahn (Summer student pattern recognition project) 
• May 2017, 2nd Workshop on Future Upgrades, Elba. agenda 
  • Slides from M. Williams (overview) 
  •  Slides from M. Obertino (Pixels with timing: the UFSD project 
  • Slides (ppt) from N. Biancacci (RF foil studies) 
• Mar 2018, 3rd Workshop on Future Upgrades, Annecy. agenda  
  • Slides from M. Williams (overview) 
  • Slides from M. Petruzzo (4D tracking studies) 
  • Slides from E. Gkougkousis (Atlas HGTD report) 
• April 2019, 4th Workshop on LHCb upgrade II, Amsterdam agenda 
  • Malcolm's slides 
  • Martin's slides  
• March 2020, 5th Workshop on LHCb upgrade II, 'Barcelona' (virtual) agenda
  • Laurent's slides (physics performance) 
  • Oscar's slides (cooling and mechanics) 
  • Kazu's slides (summary and costing) 

VELO U2 Workshops

• Mar 2018, "VELO U2 Retreat", Villars-sur-Ollon. agenda 
• Mar 2019, "VELO U2 Retreat v2", Villars-sur-Ollon. agenda 

Dedicated VELO meetings

• 4 Mar 2016 VELO Friday meeting
  • Chris Parkes: "Introduction"
  • Flavio Marchetto: "NA62 - Experience with Pixels with Timing"
  • Tony Affolder: "Radiation Hardness Constraints"
  • Marco Gersabeck: "Conservative design - geometry to survive radiation damage"
  • Jon Harrison: "Adveturous design - with pixel timing"
  • Massimiliano Fiorini: "Pixels with timing and FPGA-based track parameters"
  • Paula Collins: "SuperVELO"
• 8 Feb 2019 VELO Friday meeting 
  • Martin Van Beuzekom: "Silicon Timing"
  • Chris Parkes: "News on Upgrade II and VELO strawman design"
  • Mark Williams: "Proposal for testing 4D pattern recognition algorithms for VELO Upgrade-II"
  • Kevin Heijhoff: "Timepix3 Telescope Timing".
• 5 Apr 2019 VELO Friday meeting 
  • Misha Mikhasenko: "Impact of spatial vs Time resolution in U2 conditions"
  • Rehearsals for two TTFU Workshop talks from Martin VB. and Malcolm J.
• 19 Jul 2019 VELO Friday meeting 
  • Mark Williams: "U2 Review overview and timeline"
  • Misha Mikhasenko: "U2 reconstruction studies with Fast MC"
  • Laurent Dufour: "Timing for improved identification of detached tracks"
• 27 Sep 2019 VELO Friday meeting 
  • Tim Evans: "U2 Pattern Recognition studies"
• 1 Nov 2019 VELO Friday meeting 
  • Tim Evans: "U2 Pattern Recognition studies"
  • Misha Mikhasenko: "U2 reconstruction studies with Fast MC"
  • John Cobbledick: "The RAMP Challenge - PR studies with parameteric MC"
• 15 Nov 2019 VELO Friday meeting 
  • Adriano Lai, Alessandro Cardini: "Timespot"
• 22 Nov 2019 VELO Friday meeting 
  • Kazu Akiba: "Preparations for an Upgrade-II FTDR"
• 13 Mar 2020 VELO Friday meeting 
  • Laurent Dufour: "Timing impact on reconstrucing multi-track states"
  • Tim Evans: "U2 Pattern Recognition studies, 3D vs 4D (track and vertex)"
  • Misha Mikhasenko: "U2 reconstruction studies with Fast MC"
• 27 Mar 2020 VELO Friday meeting 
  • Laurent Dufour: "Rehearsal for U2 Workshop: Performance"
  • Oscar Francisco: "Rehearsal for U2 Workshop: Integration"
  • Kazu Akiba: "Rehearsal for U2 Workshop: Sensors and electronics"
• 24 Apr 2020 VELO Friday meeting 
  • Tim Evans: "Reconstruction Studies for LHCb VELO Upgrade-II"
  • Nicola Neri: "4D fast tracking for VELO Upgrade-II"
  • Angelo Carbone: "A fast simulation validation towards performance studies for a VELO Upgrade-II"
• 17 July 2020 Dedicated VELO U2 FastSim meeting 
  • Misha Mikhasenko: "CERN FastSim"
  • Mark Williams: "Manchester FastSim"
  • Marco Petruzzo: "Milano FastSim"
  • Angelo Carbone: "Bologna FastSim"
  • Laurent Dufour: "Exploratory ideas"
• 17 July 2020 VELO Friday meeting 
  • Serena Maccolini: "Performance studies for the Upgrade II"
  • Robbert Erik Geertsema: "IP, Decay time and SV association using time information"

Other internal LHCb presentations

• Jul 2017, Impedance meeting @CERN. agenda 
  • Slides from N. Biancacci (RF foil studies) 
• Sep 2017, LHCb Week @Lake Placid. agenda 
  • Slides from M. Williams (VELO U2 overview) 
• Oct 2017, HL-LHC Workshop @CERN. agenda 
  • Slides from M. Williams (overview) 
  • Slides from G. Ciezarek (RF foil removal impact) 
• Dec 2017, Future Upgrade focused T&A meeting. agenda 
  • Slides from M. Williams (VELO considerations) 
• Sep 2018, LHCb Week @Valencia. agenda 
  • Slides from Paula (need for, and feasibility of, timing pixels) 
• Jun 2019, LHCb Week Upgrade-II session. agenda 
  • Slides from Adriano (ASICs and sensors for U2 VELO) 
• Dec 2019, LHCb Week Upgrade-II session. agenda 
  • Slides from Paula (Hybrid Pixels for Upgrade-II) 
  • Slides from Kazu (U2 physics studies) 
• July 2020, Simulation group mini-workshop on U2 (and U1b) simulation. agenda 
  • Slides from Laurent 

VELO Upgrade-II Conference/external talks (incomplete)

• Dec 2018, PIXEL Conference  (Taipei, Taiwan): "The LHCb VELO Upgrade II" (M. Williams)
• Feb 2019, Vienna Conf. on Instrumentation  (Vienna, Austria): "The LHCb Upgrade and the VELO" (P. Collins, includes 3 slides on U2 VELO)
• Mar 2019, AIDA workshop on future of tracking  (Oxford, UK): "4-dimensional vertexing for VELO upgrade" (K. Akiba) 

Related dedicated meetings

• Oct 2017, "New Dimensions in Silicon Detectors", Manchester (IoP meeting on pixels with timing). agenda 

 

Notes on specific studies

Track Pattern recognition (3D)

Manuel Jahn (CERN summer student 2016) performed a pattern recognition study based on the Upgrade-I VELO simulation and design, but with the luminosity increased to U2 levels (2E34/cm/cm/s). He reported tracking performances for the U1 VELO, and for alternative scenarios, e.g. with the pixel pitch reduced from 55 to 27.5 microns, and/or with adjusted pattern recognition parameters.

Apart from the above presentations, his work is documented in his end-of-project report , and in the presentation he gave at the LHCb Tuesday meeting  (slides ).

More recently (2019) Tim Evans has run the latest U1 pattern recognition code over a sample of simulated events under U2 conditions. With the updates to the PR algorithm (notably the phi ordering and limited number of hits considered) the tracking performance is much improved compared to Manuel's findings in 2016. See his presentation from the VELO meeting  of 27 Sep 2019 for details (for long tracks, ghost rate 1.5%, efficiency 95.7%). For the latest news, check the most recent update at a VELo Friday meeting from Tim (see above).

Track Pattern recognition (4D)

The Milan group (N. Neri, M. Petruzzo, P. Gandini) have performed general studies on the influence of adding timing information to tracking algorithms. Specific results for an LHCb-like detector were reported in the Annecy workshop  in March 2018.

Misha Mikhasenko (2019) has developed some parametric simulation (in collaboration with others, e.g. John and Shantam from Manchester) to study the relative importance of pixel size compared to time resolution, both for physics performance and for resource use (combinatorics etc). See his presentation at the VELO meeting  of 1 Nov 2019, and subsequent VELO Friday meeting udpates, for details.

The Manchester group (plus Vava Gligorov) have two students (Cobbledick, Taneja) developed a RAMP pattern recognition challenge, with the aim to provide a set of standard data samples (with precise time information) and scoring metrics for future VELO PR studies. See presentation in VELO meeting  of 1 Nov 2019 for status and links.

The Nikhef group proposed a 4D pattern recognition project  for Google Summer of Code 2019 ( Aaij, Hynds, Raven).

Vertex Reconstruction

Tim Evans (2019) has started to investigate PV reconstruction, using a sample of full MC generated under U2 conditions, both with and without timing information in the hits. As this is a quickly-evolving study, check his most recent update at a VELO Friday meeting (above) for the latest information.

Background rejection

Laurent Dufour (2019) has investigated the performance of flight-distance based metrics (e.g. IPchi2) to select signal tracks from long-lived b hadrons, and differentiate from prompt background. This was done using full MC under realistic U2 conditions, with cheated pattern recognition. He also investigated how the addition of timing information might help. Executive summary: Efficiency for selecting signals using IPchi2 becomes worse as number of other PVs in the event increases. With 50ps timing per track, this can be mitigated to some extent. See his presentation at the VELO meeting  of 1 Nov 2019 for details.

A more sophisticated study presented on 13/3/2020 (see above) shows the potential impact on reconstructing multi-track states. As this is a quickly-evolving study, check Laurent's most recent update at a VELO Friday meeting (above) for the latest information.

PV mis-association fraction for long-lived particles, and timing

Following initial work by V. Gligorov (see TTFU presentation from Apr 2015) a number of increasingly realistic studies have been performed to determine the PV-association performance for long-lived particles, and the potential benefit of adding time information to the VELO. In particular, this was the subject of Biljana Mitreska's 2017 CERN Summer Student project, which for the first time included the option of having different timing precision in inner and outer radial regions of the VELO.

Apart from the above general presentations, this work is documented in:

• End-of-project report ,
• Tuesday meeting presentation 
• Poster presented at the 2017 HL-LHC meeting .

This work was continued by a Manchester Masters' student (Aditya Bhanderi) who among other things added a Kalman track fit to allow the influence of changing the pixel size to be studied. Later (Sep 2018) this work was continued by another CERN Summer student (Ziga Brencic), who made significant code improvements and generalised the studies to different possible channels.