Electromagnetic interactions of nuclei at the FCC-hh Igor Pshenichnov 1,*) , Sergey Gunin 1,2) 1) Institute for Nuclear Research, Russian Academy of Sciences, Moscow, Russia 2) Moscow Institute of Physics and Technology, Moscow Region, Russia *) e-mail: pshenich@inr.ru XV International Seminar on Electromagnetic Interactions of Nuclei Moscow 8-11 October 2018
Introduction ● The Higgs boson has been discovered in pp-collisions at the LHC. ● The LHC can be also tuned to collide nuclei, but with a bit lower energy per nucleon-nucleon pair: ● Physicists think of a new machine – a Future Circular Collider (FCC) - to discover particles beyond the Standard model. One of the options under consideration is a proton- proton collider (FCC-hh) also capable to collide nuclei. ● In this talk we discuss the influence of electromagnetic interactions of nuclei on the operation of the FCC-hh and lessons from the LHC on this subject. 2
http://cern.ch/fcc
M. Benedikt and F. Zimmermann, Future Circular Collider Study: Status and Plans, 3 rd FCC week, Berlin, 2017 http://cern.ch/fcc
Next 25 years of high-energy physics at CERN http://cern.ch/fcc
Outline: I. Electromagnetic interactions of nuclei at the LHC: – Bound-free pair-production (BFPP) cross section vs – Electromagnetic dissociation (EMD) of beam nuclei vs – Hadronic interactions II. Production of secondary nuclei at the LHC calculated with RELDIS model III. Possibility to measure in ALICE experiment at the LHC IV. Electromagnetic interactions of nuclei at the FCC-hh: predictions and concerns: – What are the best ion species to collide ? V. Conclusions and future work 6
I. Electromagnetic interactions of nuclei at the LHC: – Bound-free pair-production (BFPP) cross section vs – Electromagnetic dissociation (EMD) of beam nuclei vs – Hadronic interactions II. Production of secondary nuclei at the LHC calculated with RELDIS model III. Possibility to measure in ALICE experiment at the LHC IV. Electromagnetic interactions of nuclei at the FCC-hh: predictions and concerns: What are the best ion species to collide ? V. Conclusions and future work 7
Electromagnetic processes slightly changing beam ions are quite frequent in the LHC ● Bound-free e + e -- pair production (BFPP) (~270 b): 208 Pb 82+ + 208 Pb 82+ → ( 208 Pb+e — 1s,2s,2p(1/2)2p(2/3),3s ) 81+ + 208 Pb 82+ + e + ● Electromagnetic dissociation: 208 Pb 82+ + 208 Pb 82+ → 208 Pb 82+ + 207 Pb 82+ + n (~100 b) → 208 Pb 82+ + 206 Pb 82+ + 2n (~ 20 b) → 208 Pb 82+ + 205 Pb 82+ + 3n (~ 6 b) → several other channels, e.g., with proton emission ● Both BFPP and EMD change the momentum per unit charge, the magnetic rigidity: p / Z e= B ρ , where ρ is the bending radius in the magnetic field B of the LHC. ● B ρ → B ρ (1 + δ ) as a result of UPC with A 0 → A , Z 0 → Z R. Bruce et al., Phys. Rev. ST Accel. Beams 12 (2009) 071002 C. Bahamonde Castro et al., TUPMW006, Proc. of IPAC2016, Busan, Korea J.M. Jowett et al.,TUPMW028, Proc. of IPAC2016, Busan, Korea 8 P.D. Hermes et al., Nucl. Instr & Meth. A 819 (2016) 73
Hadronic cs vs EM cs at the LHC: σ had / σ tot E/A E/Z a) c) σ had σ EMD σ BFPP σ tot beams (TeV) (TeV) (b) (b) (b) (b) (%) 40 Ar 18+ 61 2.93 6.5 2.689 1.7 ~0.016 4.4 40 Ca 20+ 3.25 6.5 2.69 2. 0.034 d) 4.7 57 63 Cu 29+ 36 2.99 6.5 3.65 5.8 ~0.46 9.9 24 78 Кr 36+ 3.00 6.5 4.19 12.4 ~0.85 17.4 24 84 Kr 36+ 2.79 6.5 4.38 13.4 ~0.85 18.6 115 In 49+ 10 2.77 6.5 5.34 40.4 ~7.4 53. 129 Xe 54+ 8 2.72 6.5 5.61 b) 50.6 ~14.6 71. 208 Pb 82+ 1.6 2.51 6.36 7.66 b) 211.4 271.8 d) 491. 238 U 92+ 0.9 2.51 6.5 8.37 299. 602.2 d) 910. a) Modified abrasion-ablation (Glauber-like) model, C. Scheidenberger, et al., PRC 70 (2004) 014902 b) Glauber MC 3.0 C. Loizides et al., arXiv:1710.07098 c) RELDIS model, see I.P., Phys. Part. Nucl. 42 (2011) 215 for model description d) H. Meier et al., PRA 63 (2001) 032713, 1s-3s, 2p states, estimated as ~Z 7 for other collision species 9
I. Electromagnetic interactions of nuclei at the LHC: Bound-free pair-production (BFPP) cross section vs Electromagnetic dissociation (EMD) of beam nuclei vs Hadronic interactions II. Production of secondary nuclei at the LHC calculated with RELDIS model III. Possibility to measure in ALICE experiment at the LHC IV. Electromagnetic interactions of nuclei at the FCC-hh: predictions and concerns: – What are the best ion species to collide ? V. Conclusions and future work 10
Main concern: secondary nuclei close to 208 Pb: 206,207 Pb, 204,205,206,207 Tl, 202,204 Hg 11
Simulation of trajectories of these secondary nuclei in the LHC Distance from IP2 (ALICE) Courtesy of Tom Mertens, John Jowett (CERN) 12
According to RELDIS many other nuclei are produced in EMD of 208 Pb at the LHC From H,He to 83 Bi (see C. Scheidenberger et al., PRC 70 (2004) 014902) Note: the inclusive cross section is plotted: e.g., multiplied by the nuclide multiplicity 13
… due to various photonuclear absorption processes ∆ multiple pions QD GDR GDR E γ (MeV) n γ +(np)-->n+p ...and hadronic n π + p degrees of freedom π 0 p p π − 14 p Nuclear ...
Decay of photoexcited nuclei: nucleon evaporation, fission or multifragmentation GDR n n Mostly neutrons are p evaporated from heavy nuclei at low excitations p Statistical multifragmentation model (SMM): J.P.Bondorf et al., Phys. Rept. 257(1995)133, includes evaporation and fission models Multifragment breakup π + p is typical for light nuclei, π 0 see I.P., I. Mishustin, J. Bondorf et al., π − p PRC 57 (1998) 1920 I.P., Phys. Part. Nuclei 42(2011)215 15
I. Electromagnetic interactions of nuclei at the LHC: Bound-free pair-production (BFPP) cross section vs Electromagnetic dissociation (EMD) of beam nuclei vs Hadronic interactions II. Production of secondary nuclei at the LHC calculated with RELDIS model III. Possibility to measure in ALICE experiment at the LHC IV. Electromagnetic interactions of nuclei at the FCC-hh: predictions and concerns: What are the best ion species to collide ? V. Conclusions and future work 16
No chance to detect secondary nuclei at the LHC, but emitted nucleons can be counted instead to estimate Z and A of residual nuclei RELDIS Zero degree (forward) calorimeters have been installed in several LHC experiments. 17
Zero Degree Calorimeters (ZDC) have been used so far by ALICE, ATLAS and CMS: ● to determine the collision centrality ALICE Collaboration, Phys. Rev. C 88 (2013) 044909 ● to study EMD of lead nuclei in ultraperipheral collisions ALICE Collaboration, Phys. Rev. Lett. 109 (2012) 252302 ● to trigger ultraperipheral events with particle production V. Guzey et al., Eur. Phys. J. C 74 (2014) 2942. A.J. Baltz et al., Phys. Rev. С 80 (2009) 044902. ● to monitor the collider luminosity A.Morsch, I.P., LHC Experimental conditions, ALICE Int. note 2002-034 ALICE Collaboration, J. Phys. G: Nucl. Part. Phys. 30 (2004) 1517 ZDC can be also used to estimate the production of residual nuclei in EMD with a dedicated trigger for EM events. The cross sections to produce a single unexcited heavy residue (e.g., 207 Pb, 208 Pb) in hadronic interactions are relatively small (~ 100 mb). 18
Example: the emission of forward neutrons measured by ALICE Pb-Pb UPC EMD of only one 1.38A+1.38A TeV beam (dominant) Energy labeled in green in ZDC at the side C Mutual EMD in red (2n,2n) ALICE Collaboration, (2n,0n) PRL 109 (1n,0n) (2012)252302 Energy in ZDC at the side A (1n,1n) (0n,1n) (1n,2n) 19
Dependence on the collision energy: SPS vs LHC vs RELDIS model Data are well described by RELDIS within six orders of magnitude of γ eff . LHC Smooth and monotonic SPS energy dependence allows the extrapolation of results for the same nuclei to higher collision energy. LHC: ALICE Collaboration, SPS: ALICE-LUMI experiment, PRL 109 (2012) 252302 PRC 71 (2005) 024905 20
I. The impact of ultraperipheral collisions of nuclei on the performance of colliders: – Decay of beam intensity due to the bound-free pair- production (BFPP ) and electromagnetic dissociation (EMD) of beam nuclei; – Certain secondary nuclei (ions) from UPC can deposit heat locally and potentially cause a quenching of superconducting magnets of the LHC. II. Whether the measurements of such yields are possible? III. Yields of secondary nuclei predicted by RELDIS model. IV. Electromagnetic interactions of nuclei at the future hadron collider – FCC-hh: predictions and concerns: – Best ion species to collide at the FCC-hh ? V. Conclusions and suggestions for future work. 21
Does the registration of forward nucleons provide a reliable estimation of the residue in EMD: what about other particles (e.g., EM produced pions, multifragmentation)? Exclusive EMD channel Inclusive production of a Emission of a given given nuclide number of neutrons Channel σ (b) Nuclide σ (b) Neutron σ (b) Nucleons and a residue, multiplicity This can be measured 207 Pb + 1n 101.6 207 Pb + X 103.3 1n + 0p 103.8 A given nucleus and no other particles 206 Pb + 2n 20.34 206 Pb + X 21.3 2n + 0p 22.06 anything else 205 Pb + 3n 5.99 205 Pb + X 6.77 3n + 0p 7.53 with ZDC 204 Pb + 4n 2.88 204 Pb + X 3.45 4n + 0p 4.30 Are these cross sections fit each other ? 22
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