p. 1Mario Deile –
Recent Elastic and Total Cross-Section Measurements by
Mario Deileon behalf of the TOTEM Collaboration
EDS Blois 2019: The 18th Conference on Elastic and Diffractive ScatteringJune 23-29, 2019
ICISE, Quy Nhon, Vietnam
p. 2Mario Deile –
~1.4 GeV2
ISR
Elastic scattering – from ISR to Tevatron: Old Trends
|t|» p2 q2
ISR
p p_
p p
(COMPETE)
• Dip vs. shoulder• Dip position: shrinkage of forward peak• Any further peaks at large |t| ? Wide range of predictions.
• Evolutions stot(s), r(s) ?• No pp data after ISR• sel /stot(s) ?
p. 3Mario Deile –
The TOTEM Experiment at the LHC
IP1: ATLAS,LHCf
IP2: ALICE
IP8: LHCb,MoEDAL
IP5: CMS,TOTEM
IP7: Betatron Cleaning
IP3: MomentumCleaning
IP6: Beam Dump
IP4: RF (Acceleration)
Roman Pots: elastic & diffractive protons close to outgoing beams à Proton Trigger
Inelastic Telescopes:charged particles in inelastic events
IP5
T1: 3.1 < |h| < 4.7 , pT > 100 MeVT2: 5.3 < |h| < 6.5 , pT > 40 MeV
à Inelastic Trigger
~ 10 m~ 14 m T1 CASTOR (CMS)
HF(CMS)
T2
Experimental Setup at IP5 in Run 1[Ref.: JINST 3 (2008) S08007]
Near Far Near FarCentre
210 220
Measurement and analysis techniques covered in past presentations and in the appendix (just ask!).
• Elastic scattering @7 TeVEPL 95-41001• First stot @ 7 TeVEPL 96-21002
l stot lumi independent @ 8 TeVPRL 111-12001
l ds/dt elastic :non- exponential behaviour @ 8 TeVNPB 899-527
• r measurement @ 8 TeVEPJ C76-661
l stot lumi independent @ 2.76 TeVPoS (DIS2017) 059l stot lumi independent @ 13 TeVEur.Phys.J. C79 (2019) 103l r measurement @ 13 TeVCERN-EP-2017-335, arXiv:1812.04732,submitted to EPJC
2011
2012l stot lumi-independent @7 TeVl Elastic, inelastic cross sectionl Elastic: full t-rangeEPL 101-21004/21003/21002
2013
2015
2016
20172018
• ds/dt elastic: dip @ 13 TeVCERN-PH-EP-2018-338,arXiv:1812.08283
• ds/dt elastic: dip @ 2.76 TeVCERN-PH-EP-2018-341,arXiv:1812.08610
• data taking at 900 GeV, CNI region
History of Elastic and Total Cross-Section Measurements
p. 6Mario Deile –
Elastic Cross-Section Measurements
p
p
q
q
schematic cross-section plot
0.9 TeV0.9 TeV
2.76 TeV
2.76 TeV7 TeV
7 TeV7 TeV
7 TeV
8 TeV
8 TeV13 TeV
13 TeV
p. 7Mario Deile –
Elastic Scattering Cross-Section Measurements
Coulomb and CNI region: < ~10-3 GeV2
“Exponential” region (“Pomeron” exchange): O(10-2 GeV2) - O(10-1GeV2)Dip-bump region: ~0.4 – 1 GeV2
perturbative QCD region: > 1 GeV2
Data sets at different energies covering a wide |t| range
(bx*, by*) = (70 m, 100 m), 3 s
Optics, XRP Approach distance
b* = 11 m, 3 sb* = 11 m, 5 sb* = 11 m, 13 s
b* = 90 m, 10 s
b* = 90 m, 5 s
b* = 3.5 m, 7 sb* = 3.5 m, 18 s
b* = 1 km, 3s
b* = 90 m, 6 sb* = 2.5 km, 3 s
b* = 90 m, 5 s, 10 s
schematic cross-section plot
0.9 TeV0.9 TeV
2.76 TeV
2.76 TeV7 TeV
7 TeV7 TeV
7 TeV
8 TeV
8 TeV13 TeV
13 TeV
p. 8Mario Deile –
Elastic Scattering: Exponential Region
Coulomb and CNI region: < ~10-3 GeV2
“Exponential” region (“Pomeron” exchange): O(10-2 GeV2) - O(10-1GeV2)Dip-bump region: ~0.4 – 1 GeV2
perturbative QCD region: > 1 GeV2
p. 9Mario Deile –
Elastic Scattering: The “Exponential” Region at low |t|
Steepening increase of nuclear elastic slope B with Ös :
Up to ~ 3 TeV: compatible with simple Regge model:
Around 3 TeV: B(s) trend changes: threshold to new effects ?
E.g. multi-Pomeron exchanges: B µ ln s à (ln s)2 [A. Donnachie, P.V. Landshoff: PRD 85 (2012) 094024]
[ ] sBBttst
t ln'2')(,dd
001)(2 aaaas a +=Þ+=µ -
New measurement at 13 TeV confirms:
[EPJC 79 (2019) 103]
NEW
= | |
p. 10Mario Deile –
Elastic Scattering: The “Exponential” Region at low |t|
Data set with 7 M events (Ös = 8 TeV, b* = 90 m):0.027 GeV2 < |t| < 0.2 GeV2 ,i.e. Coulomb effects negligible
Quite exponential at the first glance,but a closer look reveals …
Is it really exponential?
Relative deviation from exponential:
Pure exponential form (Nb = 1)excluded at 7.2 s significance.
[NPB 899 (2015) 527]
... a percent-level deviation only visible with very high statistics.
refref/dd -ts
NPB 899-527
8 TeV
p. 11Mario Deile –
Elastic Scattering: The “Exponential” Region at low |t|
Non-exponentiality at |t| < 0.2 GeV2: similar pattern observed also at Ös = 7 and 13 TeV
8 TeV7 TeV
refref/dd -ts where ref = fixed
exponential functionA e-B|t|
NPB 899-527
13 TeV
Can this be due to CNI effects?(although fit region stronglydominated by nuclear amplitude)
à Include region at even lower |t| ![CERN-EP-2018-338]
NEW
schematic cross-section plot
0.9 TeV0.9 TeV
2.76 TeV
2.76 TeV7 TeV
7 TeV7 TeV
7 TeV
8 TeV
8 TeV13 TeV
13 TeV
p. 12Mario Deile –
Elastic Scattering: Coulomb and CNI Region
Coulomb and CNI region: < ~10-3 GeV2
“Exponential” region (“Pomeron” exchange): O(10-2 GeV2) - O(10-1GeV2)Dip-bump region: ~0.4 – 1 GeV2
perturbative QCD region: > 1 GeV2
p. 13Mario Deile –
Elastic Scattering: Coulomb-Nuclear Interference Region
Measure elastic scattering at |t| as low as 6 x 10-4 GeV2 (8 TeV) and 8 x 10-4 GeV2 (13 TeV)• optics specially developed for measurements at very low |t| (b* = 1 – 2.5 km)• RP approach to 3 s from the beam centre
Ös = 8 TeV, b* = 1000 m Ös = 13 TeV, b* = 2500 m
[EPJC 76 (2016) 661]
[CERN-EP-2017-335]
NEW
p. 14Mario Deile –
Simplified West-Yennie (SWY) formula (standard in the past):• constant slope B(t) = b0 à already excluded by 90m data at higher |t|à SWY incompatible with data !• constant hadronic phase arg(FH) = p0
• Y(t) acts as real interference phase
Cahn or Kundrát-Lokajíček (KL) formula:• any slope B(t)• any hadronic phase arg(FH): to be chosen as input• complex Y(t) !
Elastic Scattering: Coulomb-Nuclear Interference Region
• Modulus constrained by measurement in nucl. region: ds/dt @ A e-B(t) |t|
B(t) = b0 + b1 t + …• Phase arg(FH): very little guidance by data
Interference region: sensitivity to arg(FH)(t=0): )0(argcot)0()0( H
H
H
FFF
=ÁÂ
=r
Choice of hadronic phase arg FH(t) controlsthe behaviour in impact-parameter space (b):elastic scattering preferentially central orperipheral
p. 15Mario Deile –
Elastic Scattering: Coulomb-Nuclear Interference Region
Purely exponential hadronic amplitude
• excluded assuming a central (e.g. constant) phase
• not explicitly excluded by data if peripheral phase
Non-exponential hadronic amplitude
Both central & peripheral phase compatible with data
Same result r = 0.12± 0.03for central and peripheral phase
Study of non-exponentiality with Coulomb terms included
8 TeV 13 TeV
So far only central phases studied:
non-exponentiality confirmed.
|t|max = 0.07 GeV2
à comparison withUA4/2 (same range)
à Discussion of r(s)after stot
[EPJC 76 (2016) 661] [CERN-EP-2017-335]
NEW
schematic cross-section plot
0.9 TeV0.9 TeV
2.76 TeV
2.76 TeV7 TeV
7 TeV7 TeV
7 TeV
8 TeV
8 TeV13 TeV
13 TeV
p. 16Mario Deile –
Elastic Scattering: The Dip and Beyond
Coulomb and CNI region: < ~10-3 GeV2
“Exponential” region (“Pomeron” exchange): O(10-2 GeV2) - O(10-1GeV2)Dip-bump region: ~0.4 – 1 GeV2
perturbative QCD region: > 1 GeV2
p. 17Mario Deile –
Elastic Scattering: The Dip and Beyond
|t|dip= 0.53 GeV2
TeV7s =
TeV13s = O(109) elastic events !
No structure at high |t| beyond the dip/bump !
|t|dip= 0.47 GeV2
TeV2.76s =
Ape
rture
lim
it|t|dip= 0.61 GeV2
[CERN-EP-2018-341][CERN-EP-2018-338]
NEW NEW
p. 18Mario Deile –
Elastic Scattering: The Dip and BeyondFocus on the Dip; Comparison pp – p pbar
TeV13s =
)()(
dipbumpR
dtd
dtd
s
s
=
Joint D0 – TOTEM analysis in progress to quantify dip / shoulder difference:
• Persistence of dip+bump in pp at TeV scale:R ~ 1.7 ~ constant
• Absence of dip in ppbarR ~ 1
à Evidence for exchange of colourless C-oddthree-gluon compound state (“Odderon”)
TeV2.76s =
R = 1.7± 0.2
R = 1.77± 0.01
[CERN-EP-2018-338][CERN-EP-2018-341]
[CERN-EP-2018-341]
NEW
p. 19Mario Deile –
Total pp Cross-Section
p. 20Mario Deile –
Total Cross-Section: Methods and Results
stot = (98.0± 2.5) mb
(ρ=0.14 [COMPETE extrapolation])
different beam intensities !
June 2011: stot = (98.3± 2.8) mb [EPL 96 (2011) 21002]
Oct. 2011: stot = (98.6± 2.2) mb [EPL 101 (2013) 21002]
stot = (99.1± 4.3) mb
7 TeV (with optical theorem)
(with optical th.)(without optical theorem)
• Luminosity-independent (b* = 90 m): stot = (101.7± 2.9) mb [PRL 111(2013) 012001]• ... improved with non-exponentiality (Nb = 3): stot = (101.9± 2.1) mb [NPB 899 (2015) 527]• Combining b* = 90 m & 1 km data: Improved extrapolation of hadronic amplitude to t = 0 using CNI fit:
stot = (102.9± 2.3) mb (assuming central hadronic phase)stot = (103.0± 2.3) mb (assuming peripheral hadronic phase)
8 TeV
[EPJC 76 (2016) 661]
Luminosity-independent: stot = (84.7± 3.3) mb using r = 0.145 [COMPETE]2.76 TeV
p. 21Mario Deile –
Total Cross-Section: Methods and Results13 TeV 2 Data Sets
b* = 90 m|t| Î [0.01; 3.75] GeV2
CNI not covered,with inelastic data
b* = 2500 m|t| Î [0.0008; 0.2] GeV2
CNI covered,no inelastic data
stot = (110.6± 3.4) mb
Lumi-independent method CNI Fit
stot = (111.8± 3.2) mb, r = 0.09± 0.01
stot = (111.3± 3.2) mb, r = 0.09± 0.01
2 variants:stot = (110.3± 3.5) mb, r = 0.08(5)± 0.01stot = (109.3± 3.5) mb, r = 0.10± 0.01
(for Nb = 1)
stot = (110.5± 2.4) mb
fully independentà weighted average
NEWFirst normalisation via Coulomb!
=161 +
( ⁄ )( + )
p. 22Mario Deile –
pp Cross-Section Measurements
14 TeV:planned for LHC Run 3
900 GeV:data taken in 2018analysis in progress
~a + b ln s + c ln2 s
[EPJC 79 (2019) 103] Increase of sel / stot continues.
[EPJC 79 (2019) 103]
p. 23Mario Deile –
Ös Trends of r and Total Cross-Section
)0(argcot)0()0( H
H
H
FFF
=ÁÂ
=r
2018 data, analysis started
from CNI analysis (see earlier).
At 13 TeV : sample with very high statistics allows an unprecedented precision:
|t|max = 0.07 GeV2
à comparison withUA4/2 (same range)
The 13 TeV measurement (for both fit range choices) lies significantly (4 – 4.7 s) below the prediction.
[CERN-EP-2017-335]
p. 24Mario Deile –
Ös Trends of r and Total Cross-Section
None of COMPETE models (all without Odderon!) is able to describe simultaneously stot and r.
[CERN-EP-2017-335]
p. 25Mario Deile –
Ös Trends of r and Total Cross-Section
... or is it a hint at a slower growth of stot(Ös) at higher Ös ? (dispersion relations!)
Exchange of a colourless 3-gluon CP-odd compound state (“Odderon”) in the t-channelcould decrease r in pp collisions at large energy:
900 GeV point will have discrimination power.[CERN-EP-2017-335]
Summary & Outlook
New measurements:• 13 TeV: stot, dsel/dt from 8 x 10-4 to 3.8 GeV2 , r• 2.76 TeV: dsel/dt up to dip/bump region
Lessons:• Two pieces of evidence for “Odderon”:
- dip/bump in pp vs. shoulder in ppbar- decrease of r(Ös) at Ös > 8 TeV- still missing: glueball in s-channel
• Steepening of B(Ös) confirmed at 13 TeV• Low |t|: non-exponential structure of dsel/dt confirmed at 13 TeV• High |t|: no further structure beyond first dip/bump
Outlook:• Data at Ös=900 GeV taken in 2018:
Analysis of stot, dsel/dt, r started• Plans for LHC Run 3 @ 14 TeV:
- b* ~ 90 m run for stot (lumi-independent with new T2 detector)- b* ~ 5 – 6 km run for CNI analysis
New T2 TDR
p. 27Mario Deile –
The End
p. 28Mario Deile –
Appendix
p. 29Mario Deile –
Proton Transport and Reconstruction via Beam Optics
(x*, y*): vertex position(qx
*, qy*): emission angle: t » -p2 (qx
* 2 + qy* 2)
x = Dp/p: momentum loss (elastic case: x = 0)
RP IP5
Measured in RP Values at IP5 to be reconstructed
Excellent beam optics understanding needed.Reconstruction of proton kinematics = inversion of transport equation
Product of all lattice element matrices
* *RP y y yy L v y= Q +
* *RP x x x xx L v x D x= Q + + Lx, Ly: effective lengths (sensitivity to scattering angle)
vx, vy: magnifications (sensitivity to vertex position)Dx : dispersion (sensitivity to momentum loss); Dy ~ 0
TOTEM method: optics calibration using proton tracks [New J. Phys. 16 (2014) 103041]
Elastic Measurement Method
Collinearity of left and right proton in x and y (Example for 13 TeV)
Trigger: double arm in XRPs
Cuts: collinearity, common vertex, position-angle correlation, low x
Corrections: acceptance, efficiency (trigger, DAQ, reconstruction), smearing in t
Extrapolation to t=0 (for stot with opt. theorem):s(dNel/d|t|t=0) ~ 1.6 % s(Nel) ~ 2.3 % @ 13 TeV
Inelastic Measurement Method
T1 (CSCs)
shit ~ 1 mm
T2 (GEMs)
shit ~ 0.1 mm
Trigger: activity in T2 (either arm)
T1+T2 Acceptance ~ 92% of the inelastic rate
Experimental corrections (mostly data-driven):beam-gas background, efficiency (trigger & reconstruction), T1-only events, pileup
MC corrections for event classes invisible to T1/T2:central diffraction, rapidity gap over T2, low-mass diffraction (M< 4.6 GeV, |h| > 6.5)
s(Ninel) = 3.7% @ 13 TeV
p. 32Mario Deile –
Elastic Scattering: Coulomb-Nuclear Interference Region(Phases)
Choice of hadronic phase arg FH(t) controls the behaviour in impact-parameter space (b)
constant (central): most commonly used:á|b|ñel < á|b|ñinel
[EPJC 76 (2016) 661]
constant (central)
peripheral
arg
FH
Phase examples:
Impact parameterdistributions:
TOTEM 8 TeV data compatible with both phases (same result for r: 0.12± 0.03)à elastic pp scattering not necessarily central
0)(arg ptF =
( ) )GeV1(texp)(arg 20
010 =+= t
ttptF nz
k
0cot)0(argcot)0()0( pF
FF H
H
H
==ÁÂ
=r in both cases.
peripheral:á|b|ñel > á|b|ñinel
p. 33Mario Deile –
Elastic Scattering: The Dip and Beyond (A1)
||el / tBeAdtd -=s
|t|dip= 0.53 GeV2 ~ |t|-7.8
TeV7=s
The 7 TeV Measurements
(3 data sets at different optics and RP distances to cover max. t-range)
Comparison with 7 TeV Predictions
At the time of the first publication:No model described the TOTEM data.
pQCD (e.g. Donnachie-Landshoff): ~ |t|-8
p. 34Mario Deile –
Elastic Scattering: the Dip and beyond (A2)
The 13 TeV Measurement
data: no structure at large |t|à rules out most models
p. 35Mario Deile –
Elastic Scattering: the Dip and beyond (A3)
~1.4 GeV2
ISR
Ös = 2.76 TeV
Dip position: moves to lower |t| with increasing energy
New measurement @ 2.76 TeV, b* = 11m:very limited t-range (0.08 – 0.4 GeV2)à dip not reached
Elastic Scattering: the Dip and beyond (A4)
)()(
dipbumpR
dtd
dtd
s
s
=
p. 37Mario Deile –
pp Cross-Section Measurements: TOTEM vs. ALFA
8 TeV: tension with ATLAS-ALFA due to normalisation (elastic slopes compatible)