Rajan Gupta
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probing scalar and tensor interactions
lattice QCD calculation of ME and direct searches
lattice: calculate nucleon charges to probe new interactions
can look at same reaction at LHC (d->u+e+nu)
measurement in (ultra)cold neutron decay sensitive to new physics
parameterize with Fierz interference term, energy-dependent part of correlation between neutrino and anti-neutrino spin and momentum
relate terms above to BSM couplings
current uncertainties on charges are ~50%
goal: reduce to 10%; plot with impact of this reduction
should be able to do this with 300/fb at LHC?
low-energy measurements needed to be competitive (need 1e-4 level; now we are at 1e-3 level? big challenge for nuclear physics community)
Emanuele Mereghetti
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continuing Rajan slides
most sensitive processes: DY
issue: contributions at dim-8
need to include those terms to cross section, not done so far
1e-4 level nuclear measurement: need to control SM contributions at that level
experimental component
feedback
experimentalists at LHC on top of these analyses, expect that to continue
nuclear part: improve technology to measure suppressed terms in cross section; improve EFT calculations
Ayres: mentioned DY dim-8: not clear if LHC collaborations intend to include them; should we ask them to do this, or can use publish unfolded data?
EM: so far using published data; could be added to analysis if experimentalists convinced
Junping: how can helicity suppressed interactions be separated?
EM: look at angular distributions of leptons in DY, look at A0 and A4: scalar and vector-vector interactions give different distributions
Vladimir Livtinenko
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looking at using energy-recovery LINACs
high-energy Higgs production (ttH, ZHH)
proposal: develop lattice and simulations to explore physics in 500-600GeV c.o.m. energy
big question: how important is beam polarization in e+e- collider with c.o.m. in 90-600GeV range?
FCC-ee will not have; CLIC and ILC will, at higher energies
Ayres: there is no important physics target in which polarization is a must; it makes some measurements more efficient
at the end it is tradeoff: with polarization you may lose luminosity, but improve efficiency, and the two balance
e.g., H production from W fusion (only left-handed W used)
Jakob Beyer: mentioning 90GeV; at Z pole, polarization does give qualitative difference, can do different measurements; this seen to be relevant in comparison between
CLIC and LEP
Ayres: could do with AFB?
Tania Roberts: 500-600GeV: would probably look at TDR of CLIC and ILC, many studies of polarized beams
https://arxiv.org/abs/2012.11267
Ayres: there is a 15-yr old report on polarization
https://arxiv.org/abs/hep-ph/0507011
Junping: role of polarization could be different if there is new physics present; would help probing nature of new physics
Junmou Chen
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2->3 VBS and Higgs self-coupling measurements
look at VLVL->VLVLH and VLVL->HHH
focus on c6 operators, w/ one, three or no propagator
w/ 3 operators: have two scales appearing at high energy, one from SM, one from BSM coupling
BSM and SM amplitudes scale (roughly) like squared ratio of scales: in high-energy limit, BSM becomes dominant
note non particularly strong enhancement in VV->VVH compared to VV->HHH
full simulation, problem and solution
transverse polarization dominates cross section -> select longitudinal polarization only for final states
enhancement of cross section of VV->VVH partly cancelled by log enhancement of SM cross section -> make pT cuts
some results from simulation: cross section vs energy
general conclusion: cross sections generally increase with c.o.m., but remain small until 5TeV -> this makes them useful only for high-energy muon collider?
looked also at pp->jjWWH
similar results, cross sections not very large at 14TeV, but sizable at 100TeV; in general, smaller cross sections and smaller enhancement than in ee case
HHH case: cross section smaller than WWH, but larger enhancement with energy
bottom line: 2->3 VBS excellent channel for Higgs self-coupling study, but only at high energy
amplitudes increase with square of energy
can look at 5-point scalar vertices from c6 operators
similar behavior of cross section in pp machine
feedback from community: no particular need now, probably when finishing project
Junping: for simulation: would like to request any MC from Snowmass MC TF?
JC: probably, will look into them
Gianfranco Morello
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mu-RWELL technology
micro-resistive WELL is a micro-pattern gaseous detector
compact, simple, with intrinsic spark protection (resistive layer from GEM used to quench sparks)
resistive layer harms rate capability -> different charge evacuation schemes
low-rate version: single resistive layer (SRL_
use 500-600V, holes in active are work as ionization chambers
limitation in area: depends on distance from the center of layer
high-rate versions: DRL (double layer) and SG (silver grid)
DLR: use two layers, with matrix of vias to connect them (1cm^2); hard to produce industrially; a 3D charge evacuation scheme
SG: 2D evacuation, easier to produce industrially
prototypes built and tested (at PSI)
rate capability: 5-10MHz/cm^2 (actually, could be higher? spot at beam line was not covering full area?)
gain: up to 1e4
space resolution <100um
efficiency: 98%
proponing to install low-rate version in CePC/FCC-ee IDEA (preshower and muon detector)
test beam at CERN H8 NA
building narrow prototypes, 50cm long (the IDEA layers will be 50x50cm^2)
competition between TPC and mu-RWELL for SCT apparatus (CREMLIN)
low-rate application for neutron detections: different cathode geometry or addition of Boron
GEANT4 simulations on going
high-rate application for LHCb muon station at HL-LHC
would need about 600 detectors -> need interaction with industry
Sam Lane
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EW restoration at LHC: VH channel
goal: look at HZ process and compare to HG: test Goldstone boson equivalence
parton level results: cross section longitudinally dominated
(look at VH helicity dependence)
look at SM VH cross section and EW-restored GH cross section
simulation, cut on DNN output to separate S and B
use MG5/PYTHIA/DELPHES
plots of pT(H)
signal strength in 1-lepton case
strength uncertainty (of all channels combined) 40% LHC and 6% at HE-LHC
chi2 vs pT(H) troubles: statistical uncertainty at high pT hides problems
looking at KL divergence, as better estimator: shows that the two hypotheses are in agreement
Ayres: what would you say if LHC measurement indicated deviations?
SL: would interpret as breakdown of EW symmetry at that energy
Ayres: sharp question: there is physics BSM, would this prove that NP is due to different ways of EW breaking?
Ian Lewis: started thinking about this
Junping: at higher pT, statistical uncertainty higher... which part of spectrum dominates contribution?
SL: first bin has indeed big effect
Junping: does this mean not helpful to go to high energy?
Samuel Homiller
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SMEFT fits (https://arxiv.org/abs/2007.01296 https://arxiv.org/abs/2102.02823)
SMEFT: playing more and more relevant role, as we do not see clear signals of NP
updated global fit in 2007.01296
new: full NLO QCD corrections in SMEFT for VH and VV
leading log NLO corrections
NLO effects do matter: they affect bins that give the most constraining power
effect of QCD corrections and anomalous couplings do not commute: important to use full predictions of SMEFT
strategy:
integrate out new particles at matching scale (few TeV)
generate subset of SMEFT coefficiencts
evolve coefficients down to EW scale (numerical changes can have significant effect on limits; new operators may also appear)
fit to H, diboson, EWPO data at EW scale and set limits on physical parameters
walked through procedure for a few models in recent paper
new work w/ goal: understand numerical importance of 1-loop matching effects (in singlet-model)
tree-level results
see that 1-loop can change by ~10% effect of tree-level result, except when large values of portal coupling
list of open questions:
- understand linear vs quadratic approximations
- compare effect of dim-8
- include top data
- include complete 1-loop matching to other models, more NLO...
Junping: there is EF04 group doing global fit
Richard Ruiz
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physics simulation at multi-TeV muon collider
big question: why mu collider now
mu collider probe muon flavor itself, beside business of energy and cleanliness
novel R&D shows that O(10TeV) muon collider are feasible
context of EF04: partonic collisions at Q~O(10TeV) we look at when electroweak symmetry is nearly restored (mW,mZ/Q->0)
details of MadGraph developments relevant to mu collider
looked at VBS and VBF vs s-channel
multi-TeV mu collider can be seen as vector boson collider
sigma(VBF) becomes more relevant than s-channel mu+mu- above 3-5TeV
same trend in the case of multi-boson production
done systematic study, this behavior seems universal
new: effective vector boson approximation (EVA)
should come out in a couple of months
idea is to consider W and Z, at high Q, as partons, and treat them as gluons in QCD: W/Z PDF to be released soon in MG5
complication in polarization to be addressed/discussed, but still putting this in MG5
VV production example
importance of longitudinal vs transverse depends on number of H
bottom line: now polarized scattering amplitudes can be done with MG5
Alessandro Tricoli: approach of W/Z PDF: what interplay/advantage with respect to calculating (with resummation) the V scattering?
RR: advantages: numerical stability (avoid large logarithms), anticipating availability of fully-resummed EW PDF, now sort of fool-proofing MG5
unclear to what extent accuracies of un-resummed EW PDF, resummed ones, and partial ME calculations compare with full ME calculation (terms, for example, from DGLAP
evolution...)
this is subtle aspect being investigated
Veena Balakrishnan
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VBS scattering
looking at dim-8 operators
focus on 3, 6, and 10TeV samples; would then look at 30TeV
final states: WWZG
not possible to separate s-channel and VBS
look for BSM signal, with interference and quadratic term added to SM signal
cross sections have non-trivial sqrt(s) dependence, some complication with MC generation
look at dilepton mass in simulation
another state: WWWW
used MG5, 5k events
calculated SM, interference, and quadratic terms to cross section; compared their addition (after separate calculation) and the complete calculation with all terms: match
at high energy, not so much in 3TeV case?
questions:
- which c.o.m. energies to consider
- leptonic vs hadronic modes
- VBS vs s-channel?
- effect of detector acceptance on sensitivity
- want to check cross sections with WHIZARD
Ayres: about energies: we have official table
Alessandro Tricoli: shall post (3,10,14,25,30 for muon, and some benchmarks for luminosity; slide 19 in
https://indico.fnal.gov/event/44870/contributions/198445/attachments/135764/168821/EFintro_CPM_Oct2020.pdf)
Richard Ruiz: question about fiducial cuts for muon collider detectors: will we have "official" set?
Ayres: eta acceptance probably smaller than ILC detector (10deg from beam)
John Stupak: there is a baseline DELPHES card for muon collider MC (https://github.com/delphes/delphes/blob/master/cards/delphes_card_MuonColliderDet.tcl)
Tania Roberts: there was a discussion last week about integrated luminosity
Alessandro Tricoli: table discussed with accelerator people as well
seems that agreement about energy is ok, unclear luminosity?
issue of discussion: luminosity declared for 30TeV is not realistic (in Alessandro's link)
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