Recent Elastic and Total Cross-Section Measurements by · EPL 96-21002 l stot lumi independent @ 8 TeV PRL 111-12001 l ds/dt elastic: non- exponential behaviour @ 8 TeV NPB 899-527

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


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




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 –


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



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


0.9 TeV0.9 TeV

2.76 TeV

2.76 TeV7 TeV

7 TeV7 TeV

7 TeV

8 TeV

8 TeV13 TeV

13 TeV


Elastic Scattering: Coulomb and CNI Region





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


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) !


• 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



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


0.9 TeV0.9 TeV

2.76 TeV

2.76 TeV7 TeV

7 TeV7 TeV

7 TeV

8 TeV

8 TeV13 TeV

13 TeV


Elastic Scattering: The Dip and Beyond





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


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


Total pp Cross-Section


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


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 +

( ⁄ )( + )


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]


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]



None of COMPETE models (all without Odderon!) is able to describe simultaneously stot and r.

[CERN-EP-2017-335]



... 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


The End


Appendix


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


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


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


Elastic Scattering: the Dip and beyond (A2)

The 13 TeV Measurement

data: no structure at large |t|à rules out most models



~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


)()(

dipbumpR

dtd

dtd

s

s

=


pp Cross-Section Measurements: TOTEM vs. ALFA

8 TeV: tension with ATLAS-ALFA due to normalisation (elastic slopes compatible)

Documents

Recent Elastic and Total Cross-Section Measurements by · EPL 96-21002 l stot lumi independent @ 8 TeV PRL 111-12001 l ds/dt elastic: non- exponential behaviour @ 8 TeV NPB 899-527