1. Christof Roland Ions at FCC, Jan 29 2014 1 Prospects for jet measurements at HL-LHC with CMS Ions at the Future Hadron Collider Meeting 29 January 2014 Christof Roland/MIT

2. Christof Roland Ions at FCC, Jan 29 2014 2 Heavy Ion Projections for HL-LHC Disclaimer: –Due to the QM preparation we can not allocate manpower or computing resources to FCC studies now –All material shown today is from the document prepared for the ECFA meeting in Aix-les-bains last year Documentation –PAS (FTR-13-025) on CDS http://cds.cern.ch/record/1610789?ln=en –Twiki with figures: https://twiki.cern.ch/twiki/bin/view/CMS/FTR-13-025

3. Christof Roland Ions at FCC, Jan 29 2014 3 Overview of FTR-13 Studies in: –hadron spectra –high-p T probes and jets –(quarkonia) –electroweak bosons Frontiers explored: –p T reach: spectra, jets, b-jets, electroweak –(most peripheral: quarkonia, dijets, spectra) –event-shape engineering: dijets, quarkonia –new rare probes: ttbar Extrapolations based on yields observed in the currently available dataset + x T scaling

4. Christof Roland Ions at FCC, Jan 29 2014 4 HI program timeline Rate: ~30kHz~50kHz>50kHz New Tracker -Extended Coverage |  |<4 New Forward calorimetry 1 MHz DAQ HL-LHC New Machine! HL-LHC for HI CMS:

5. Christof Roland Ions at FCC, Jan 29 2014 5 HI program timeline -Updated Schedule Rate: ~30kHz~50kHz>50kHz New Tracker -Extended Coverage |  |<4 New Forward calorimetry 1 MHz DAQ HL-LHC New Machine! HL-LHC for HI CMS: Pixel detector upgrade 3 Layers -> 4 Layers LS2 LS3

6. Christof Roland Ions at FCC, Jan 29 2014 6 High p T Hadrons Charged particle spectra –Use Pythia ProQ20 Cross section for pThat=380 at 5.5 TeV: σ=0.14 nb –61k events in 10nb -1 5.5 TeV PbPb collisions generate this number of events to illustrate p T reach Add other p T hat samples for a realistic p T spectrum –Leading-order only –Experimentally easily accessible with jet or track triggers

7. Christof Roland Ions at FCC, Jan 29 2014 7 Plenty of dijet events in 10/nb: After p T selection, select dijets based on: centrality (0-10%): 30% of dijets v2 : 10% event-plane angle: 25% result: 0.0075 of dijets in a single bin Dijets: Event-shape engineering 10/nb expectation obtained by randomly using events in the current dijet sample corresponding to the relevant statistics The leading jet cut is 180 GeV so that the surface bias due to missing away side jet is reduced.

8. Christof Roland Ions at FCC, Jan 29 2014 8 b-tagged Dijets Estimated yield of doubly tagged b-dijets Select dijet sample from current PbPb data to represent 10/nb.

9. Christof Roland Ions at FCC, Jan 29 2014 9 Colorless Probes Estimated from pure Pythia (unquenched) simulations at 5.5 TeV for the estimated statistics. Z+Jet  +Jet

10. Christof Roland Ions at FCC, Jan 29 2014 10 Summary – High-p T Probes

11. Christof Roland Ions at FCC, Jan 29 2014 11 Summary of Electroweak Bosons 9/21/2015 FTR-13-025 11

12. Christof Roland Ions at FCC, Jan 29 2014 12 Jet Reconstruction in CMS Reconstruct physics objects from detector signals –Tracks+Calo Clusters -> Hadrons, Photons, Muons etc Particle momentum from high precision tracking –Jet Finding Apply underlying event subtraction Cluster physics objects

13. Christof Roland Ions at FCC, Jan 29 2014 13 Some considerations on Jet Reco Expected HI HL-LHC jet reco performance –Assumption: Future HI =~ Current pp Improved tracking performance to help particle flow reco Significant improvement from 4 layer pixel system Finite tracking efficiency in HI is currently the limiting factor in the jet reconstruction performance (in CMS) Modulo irreducible underlying event fluctuations Expect only a moderate increase in event multiplicity from 2.76 to 5.1 TeV Underlying event subtraction significant room for improvement over current Iterative Pileup algorithm e.g. the Voronoi subtraction method Uses the full PF candidate granularity and explicitly accounts for the azimuthal anisotropy of the events

14. Christof Roland Ions at FCC, Jan 29 2014 14 Pb top quark ttbar events –Decay before thermalization – probe very early stages of medium –Alternative channel for b-quark energy loss Decay channels –ll+bb+MET 10%: “observation channel” –l+bb+2jet+MET 44% –bb+4jet 46% Estimated production rate –81pb at 5.5 TeV pp (http://www.lpthe.jussieu.fr/~cacciari/ttbar/)http://www.lpthe.jussieu.fr/~cacciari/ttbar/ –10 nb-1 5.5 TeV PbPb collisions -> 35k ttbar events –Branching ratio into e + e -, u + u - and e +- u +- ~ 6.5% -> ~2300 ttbar –Current CMS (pp) acc∙eff ~ 23% -> ~500 pairs –In PbPb Lepton reco efficiency ~100% (now) Somewhat lower b-tagging efficiency (close to pp with upgrade) Larger background -> Lower MET resolution (depends on mult)

15. Christof Roland Ions at FCC, Jan 29 2014 15 Jet Reco considerations at FCC Consider CMS tracker + ATLAS Calorimetry –CMS style particle flow reconstruction combined with ATLAS style calorimetry (longitudinal segmentation) Should give significant improvement over current setups for HI Should be a conservative assumption for the performance of future experiments –Multiplicity evolution PbPb dn/d  evolution steeper than log(sqrt(s)) Extrapolation to FCC energies non trivial –Compensate with lighter ions? Potentially higher inst parton luminosity More managable backgrounds Joint pp+HI experiment? –Construction cost favorable –Key ingredient to e.g. top reco performance is the data driven calibration Need full pp lumi for calibration for HI

16. Christof Roland Ions at FCC, Jan 29 2014 16 Conclusion The capacity to reconstruct HEP like high p T physics objects in HI has been well demonstrated by the current LHC experiments –Reliably reconstruct Jets, Z, W, MET, b-Jets etc –Expect increased reconstruction performance with the Stage 2 CMS and ATLAS detectors –Rich jet physics program at HL-LHC FCC physics program –Based on the assumption of a joint pp+HI detector setup we can expect excellent capability to fully exploit HEP style physics signatures (top, higgs?) in HI

17. Christof Roland Ions at FCC, Jan 29 2014 17 9/21/201517 Backup slides FTR-13-025

18. Christof Roland Ions at FCC, Jan 29 2014 18 The Voronoi Algorithm https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsDPSUESubtractionPF

19. Christof Roland Ions at FCC, Jan 29 2014 19 A factor 2 increase in √s NN : –Estimation of the √S NN impact on the cross-sections: For ϒ (1S): –From BPH-10-003 σ pp ( ϒ (1S)) at 7TeV = 8.3 nb –From HIN-10-006 R AA = 0.63 dn/dy / T AA (PbPb) = 0.485 then dσ/dy (pp) = 0.485 / 0.63 = 0.77 σ pp ( ϒ (1S)) at 2.76TeV = dσ/dy (pp) x 4 (rap. unit) = 3.1 nb  The scaling factor from 2.76 to 7 TeV for ϒ (1S) is : 8.3nb / 3.1nb = 2.7 For J/ψ:  The scaling factor from 2.76 to 7 TeV for the J/ψ is : 71nb /29nb = 2.45 For 5.5 TeV, we roughly took 2 Ignore the centrality dependent suppression (conservative estimate) 9/21/2015 FTR-13-025 19 Assumptions for dilepton projections

20. Christof Roland Ions at FCC, Jan 29 2014 20 Dilepton projections for 10 nb -1 and 5.5 TeV Yields 10nb-1 [0-100%] = Yields 150 μb-1 [0-100%] x Factor Lumi (66,66)x Factor √SNN (2) Yields 10nb-1 [x-100%] = Yields 10nb-1 [0-100%] * ( 〈 Ncoll(x–100%) 〉 ∕ 〈 Ncoll(0–100%) 〉 ) x binwidth Example - for Y(1S) : Yields 10nb-1 [0-100%] (Y(1S))= 2000*66,66*2 *30 = 26667 Yields 10nb-1 [50-100%] = (26667*30 / 363)*0.5 9/21/2015 FTR-13-025 20

21. Christof Roland Ions at FCC, Jan 29 2014 21 Summary of Quarkonia 9/21/2015 FTR-13-025 21

22. Christof Roland Ions at FCC, Jan 29 2014 22 9/21/2015FTR-13-02522

23. Christof Roland Ions at FCC, Jan 29 2014 23 9/21/201523 ProQ20 ● Pythia ProQ20 was found to give a good description of the charged particle spectrum at high-p T HIN-10-005QCD-10-008 FTR-13-025